summaryrefslogtreecommitdiff
path: root/drivers/char/tty_io.c
blob: 49c1a2267a55c7490c504ba7486b276575851ae8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
/*
 *  linux/drivers/char/tty_io.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
 * or rs-channels. It also implements echoing, cooked mode etc.
 *
 * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
 *
 * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
 * tty_struct and tty_queue structures.  Previously there was an array
 * of 256 tty_struct's which was statically allocated, and the
 * tty_queue structures were allocated at boot time.  Both are now
 * dynamically allocated only when the tty is open.
 *
 * Also restructured routines so that there is more of a separation
 * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
 * the low-level tty routines (serial.c, pty.c, console.c).  This
 * makes for cleaner and more compact code.  -TYT, 9/17/92
 *
 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
 * which can be dynamically activated and de-activated by the line
 * discipline handling modules (like SLIP).
 *
 * NOTE: pay no attention to the line discipline code (yet); its
 * interface is still subject to change in this version...
 * -- TYT, 1/31/92
 *
 * Added functionality to the OPOST tty handling.  No delays, but all
 * other bits should be there.
 *	-- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
 *
 * Rewrote canonical mode and added more termios flags.
 * 	-- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
 *
 * Reorganized FASYNC support so mouse code can share it.
 *	-- ctm@ardi.com, 9Sep95
 *
 * New TIOCLINUX variants added.
 *	-- mj@k332.feld.cvut.cz, 19-Nov-95
 *
 * Restrict vt switching via ioctl()
 *      -- grif@cs.ucr.edu, 5-Dec-95
 *
 * Move console and virtual terminal code to more appropriate files,
 * implement CONFIG_VT and generalize console device interface.
 *	-- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
 *
 * Rewrote init_dev and release_dev to eliminate races.
 *	-- Bill Hawes <whawes@star.net>, June 97
 *
 * Added devfs support.
 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 13-Jan-1998
 *
 * Added support for a Unix98-style ptmx device.
 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
 *
 * Reduced memory usage for older ARM systems
 *      -- Russell King <rmk@arm.linux.org.uk>
 *
 * Move do_SAK() into process context.  Less stack use in devfs functions.
 * alloc_tty_struct() always uses kmalloc()
 *			 -- Andrew Morton <andrewm@uow.edu.eu> 17Mar01
 */

#include <linux/types.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/devpts_fs.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/console.h>
#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/kd.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/delay.h>

#include <asm/uaccess.h>
#include <asm/system.h>

#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/selection.h>

#include <linux/kmod.h>
#include <linux/nsproxy.h>

#undef TTY_DEBUG_HANGUP

#define TTY_PARANOIA_CHECK 1
#define CHECK_TTY_COUNT 1

struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC,
	.c_ispeed = 38400,
	.c_ospeed = 38400
};

EXPORT_SYMBOL(tty_std_termios);

/* This list gets poked at by procfs and various bits of boot up code. This
   could do with some rationalisation such as pulling the tty proc function
   into this file */

LIST_HEAD(tty_drivers);			/* linked list of tty drivers */

/* Mutex to protect creating and releasing a tty. This is shared with
   vt.c for deeply disgusting hack reasons */
DEFINE_MUTEX(tty_mutex);
EXPORT_SYMBOL(tty_mutex);

#ifdef CONFIG_UNIX98_PTYS
extern struct tty_driver *ptm_driver;	/* Unix98 pty masters; for /dev/ptmx */
static int ptmx_open(struct inode *, struct file *);
#endif

static void initialize_tty_struct(struct tty_struct *tty);

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);
ssize_t redirected_tty_write(struct file *, const char __user *,
							size_t, loff_t *);
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *);
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
#ifdef CONFIG_COMPAT
static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg);
#else
#define tty_compat_ioctl NULL
#endif
static int tty_fasync(int fd, struct file *filp, int on);
static void release_tty(struct tty_struct *tty, int idx);
static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);
static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);

/**
 *	alloc_tty_struct	-	allocate a tty object
 *
 *	Return a new empty tty structure. The data fields have not
 *	been initialized in any way but has been zeroed
 *
 *	Locking: none
 */

static struct tty_struct *alloc_tty_struct(void)
{
	return kzalloc(sizeof(struct tty_struct), GFP_KERNEL);
}

static void tty_buffer_free_all(struct tty_struct *);

/**
 *	free_tty_struct		-	free a disused tty
 *	@tty: tty struct to free
 *
 *	Free the write buffers, tty queue and tty memory itself.
 *
 *	Locking: none. Must be called after tty is definitely unused
 */

static inline void free_tty_struct(struct tty_struct *tty)
{
	kfree(tty->write_buf);
	tty_buffer_free_all(tty);
	kfree(tty);
}

#define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)

/**
 *	tty_name	-	return tty naming
 *	@tty: tty structure
 *	@buf: buffer for output
 *
 *	Convert a tty structure into a name. The name reflects the kernel
 *	naming policy and if udev is in use may not reflect user space
 *
 *	Locking: none
 */

char *tty_name(struct tty_struct *tty, char *buf)
{
	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
		strcpy(buf, "NULL tty");
	else
		strcpy(buf, tty->name);
	return buf;
}

EXPORT_SYMBOL(tty_name);

int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
			      const char *routine)
{
#ifdef TTY_PARANOIA_CHECK
	if (!tty) {
		printk(KERN_WARNING
			"null TTY for (%d:%d) in %s\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
	if (tty->magic != TTY_MAGIC) {
		printk(KERN_WARNING
			"bad magic number for tty struct (%d:%d) in %s\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
#endif
	return 0;
}

static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT
	struct list_head *p;
	int count = 0;

	file_list_lock();
	list_for_each(p, &tty->tty_files) {
		count++;
	}
	file_list_unlock();
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_SLAVE &&
	    tty->link && tty->link->count)
		count++;
	if (tty->count != count) {
		printk(KERN_WARNING "Warning: dev (%s) tty->count(%d) "
				    "!= #fd's(%d) in %s\n",
		       tty->name, tty->count, count, routine);
		return count;
	}
#endif
	return 0;
}

/*
 * Tty buffer allocation management
 */

/**
 *	tty_buffer_free_all		-	free buffers used by a tty
 *	@tty: tty to free from
 *
 *	Remove all the buffers pending on a tty whether queued with data
 *	or in the free ring. Must be called when the tty is no longer in use
 *
 *	Locking: none
 */

static void tty_buffer_free_all(struct tty_struct *tty)
{
	struct tty_buffer *thead;
	while ((thead = tty->buf.head) != NULL) {
		tty->buf.head = thead->next;
		kfree(thead);
	}
	while ((thead = tty->buf.free) != NULL) {
		tty->buf.free = thead->next;
		kfree(thead);
	}
	tty->buf.tail = NULL;
	tty->buf.memory_used = 0;
}

/**
 *	tty_buffer_init		-	prepare a tty buffer structure
 *	@tty: tty to initialise
 *
 *	Set up the initial state of the buffer management for a tty device.
 *	Must be called before the other tty buffer functions are used.
 *
 *	Locking: none
 */

static void tty_buffer_init(struct tty_struct *tty)
{
	spin_lock_init(&tty->buf.lock);
	tty->buf.head = NULL;
	tty->buf.tail = NULL;
	tty->buf.free = NULL;
	tty->buf.memory_used = 0;
}

/**
 *	tty_buffer_alloc	-	allocate a tty buffer
 *	@tty: tty device
 *	@size: desired size (characters)
 *
 *	Allocate a new tty buffer to hold the desired number of characters.
 *	Return NULL if out of memory or the allocation would exceed the
 *	per device queue
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
{
	struct tty_buffer *p;

	if (tty->buf.memory_used + size > 65536)
		return NULL;
	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
	if (p == NULL)
		return NULL;
	p->used = 0;
	p->size = size;
	p->next = NULL;
	p->commit = 0;
	p->read = 0;
	p->char_buf_ptr = (char *)(p->data);
	p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
	tty->buf.memory_used += size;
	return p;
}

/**
 *	tty_buffer_free		-	free a tty buffer
 *	@tty: tty owning the buffer
 *	@b: the buffer to free
 *
 *	Free a tty buffer, or add it to the free list according to our
 *	internal strategy
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
{
	/* Dumb strategy for now - should keep some stats */
	tty->buf.memory_used -= b->size;
	WARN_ON(tty->buf.memory_used < 0);

	if (b->size >= 512)
		kfree(b);
	else {
		b->next = tty->buf.free;
		tty->buf.free = b;
	}
}

/**
 *	__tty_buffer_flush		-	flush full tty buffers
 *	@tty: tty to flush
 *
 *	flush all the buffers containing receive data. Caller must
 *	hold the buffer lock and must have ensured no parallel flush to
 *	ldisc is running.
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static void __tty_buffer_flush(struct tty_struct *tty)
{
	struct tty_buffer *thead;

	while ((thead = tty->buf.head) != NULL) {
		tty->buf.head = thead->next;
		tty_buffer_free(tty, thead);
	}
	tty->buf.tail = NULL;
}

/**
 *	tty_buffer_flush		-	flush full tty buffers
 *	@tty: tty to flush
 *
 *	flush all the buffers containing receive data. If the buffer is
 *	being processed by flush_to_ldisc then we defer the processing
 *	to that function
 *
 *	Locking: none
 */

static void tty_buffer_flush(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->buf.lock, flags);

	/* If the data is being pushed to the tty layer then we can't
	   process it here. Instead set a flag and the flush_to_ldisc
	   path will process the flush request before it exits */
	if (test_bit(TTY_FLUSHING, &tty->flags)) {
		set_bit(TTY_FLUSHPENDING, &tty->flags);
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		wait_event(tty->read_wait,
				test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
		return;
	} else
		__tty_buffer_flush(tty);
	spin_unlock_irqrestore(&tty->buf.lock, flags);
}

/**
 *	tty_buffer_find		-	find a free tty buffer
 *	@tty: tty owning the buffer
 *	@size: characters wanted
 *
 *	Locate an existing suitable tty buffer or if we are lacking one then
 *	allocate a new one. We round our buffers off in 256 character chunks
 *	to get better allocation behaviour.
 *
 *	Locking: Caller must hold tty->buf.lock
 */

static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
{
	struct tty_buffer **tbh = &tty->buf.free;
	while ((*tbh) != NULL) {
		struct tty_buffer *t = *tbh;
		if (t->size >= size) {
			*tbh = t->next;
			t->next = NULL;
			t->used = 0;
			t->commit = 0;
			t->read = 0;
			tty->buf.memory_used += t->size;
			return t;
		}
		tbh = &((*tbh)->next);
	}
	/* Round the buffer size out */
	size = (size + 0xFF) & ~0xFF;
	return tty_buffer_alloc(tty, size);
	/* Should possibly check if this fails for the largest buffer we
	   have queued and recycle that ? */
}

/**
 *	tty_buffer_request_room		-	grow tty buffer if needed
 *	@tty: tty structure
 *	@size: size desired
 *
 *	Make at least size bytes of linear space available for the tty
 *	buffer. If we fail return the size we managed to find.
 *
 *	Locking: Takes tty->buf.lock
 */
int tty_buffer_request_room(struct tty_struct *tty, size_t size)
{
	struct tty_buffer *b, *n;
	int left;
	unsigned long flags;

	spin_lock_irqsave(&tty->buf.lock, flags);

	/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
	   remove this conditional if its worth it. This would be invisible
	   to the callers */
	if ((b = tty->buf.tail) != NULL)
		left = b->size - b->used;
	else
		left = 0;

	if (left < size) {
		/* This is the slow path - looking for new buffers to use */
		if ((n = tty_buffer_find(tty, size)) != NULL) {
			if (b != NULL) {
				b->next = n;
				b->commit = b->used;
			} else
				tty->buf.head = n;
			tty->buf.tail = n;
		} else
			size = left;
	}

	spin_unlock_irqrestore(&tty->buf.lock, flags);
	return size;
}
EXPORT_SYMBOL_GPL(tty_buffer_request_room);

/**
 *	tty_insert_flip_string	-	Add characters to the tty buffer
 *	@tty: tty structure
 *	@chars: characters
 *	@size: size
 *
 *	Queue a series of bytes to the tty buffering. All the characters
 *	passed are marked as without error. Returns the number added.
 *
 *	Locking: Called functions may take tty->buf.lock
 */

int tty_insert_flip_string(struct tty_struct *tty, const unsigned char *chars,
				size_t size)
{
	int copied = 0;
	do {
		int space = tty_buffer_request_room(tty, size - copied);
		struct tty_buffer *tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0))
			break;
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
		copied += space;
		chars += space;
		/* There is a small chance that we need to split the data over
		   several buffers. If this is the case we must loop */
	} while (unlikely(size > copied));
	return copied;
}
EXPORT_SYMBOL(tty_insert_flip_string);

/**
 *	tty_insert_flip_string_flags	-	Add characters to the tty buffer
 *	@tty: tty structure
 *	@chars: characters
 *	@flags: flag bytes
 *	@size: size
 *
 *	Queue a series of bytes to the tty buffering. For each character
 *	the flags array indicates the status of the character. Returns the
 *	number added.
 *
 *	Locking: Called functions may take tty->buf.lock
 */

int tty_insert_flip_string_flags(struct tty_struct *tty,
		const unsigned char *chars, const char *flags, size_t size)
{
	int copied = 0;
	do {
		int space = tty_buffer_request_room(tty, size - copied);
		struct tty_buffer *tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0))
			break;
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memcpy(tb->flag_buf_ptr + tb->used, flags, space);
		tb->used += space;
		copied += space;
		chars += space;
		flags += space;
		/* There is a small chance that we need to split the data over
		   several buffers. If this is the case we must loop */
	} while (unlikely(size > copied));
	return copied;
}
EXPORT_SYMBOL(tty_insert_flip_string_flags);

/**
 *	tty_schedule_flip	-	push characters to ldisc
 *	@tty: tty to push from
 *
 *	Takes any pending buffers and transfers their ownership to the
 *	ldisc side of the queue. It then schedules those characters for
 *	processing by the line discipline.
 *
 *	Locking: Takes tty->buf.lock
 */

void tty_schedule_flip(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->buf.lock, flags);
	if (tty->buf.tail != NULL)
		tty->buf.tail->commit = tty->buf.tail->used;
	spin_unlock_irqrestore(&tty->buf.lock, flags);
	schedule_delayed_work(&tty->buf.work, 1);
}
EXPORT_SYMBOL(tty_schedule_flip);

/**
 *	tty_prepare_flip_string		-	make room for characters
 *	@tty: tty
 *	@chars: return pointer for character write area
 *	@size: desired size
 *
 *	Prepare a block of space in the buffer for data. Returns the length
 *	available and buffer pointer to the space which is now allocated and
 *	accounted for as ready for normal characters. This is used for drivers
 *	that need their own block copy routines into the buffer. There is no
 *	guarantee the buffer is a DMA target!
 *
 *	Locking: May call functions taking tty->buf.lock
 */

int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
								size_t size)
{
	int space = tty_buffer_request_room(tty, size);
	if (likely(space)) {
		struct tty_buffer *tb = tty->buf.tail;
		*chars = tb->char_buf_ptr + tb->used;
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
	}
	return space;
}

EXPORT_SYMBOL_GPL(tty_prepare_flip_string);

/**
 *	tty_prepare_flip_string_flags	-	make room for characters
 *	@tty: tty
 *	@chars: return pointer for character write area
 *	@flags: return pointer for status flag write area
 *	@size: desired size
 *
 *	Prepare a block of space in the buffer for data. Returns the length
 *	available and buffer pointer to the space which is now allocated and
 *	accounted for as ready for characters. This is used for drivers
 *	that need their own block copy routines into the buffer. There is no
 *	guarantee the buffer is a DMA target!
 *
 *	Locking: May call functions taking tty->buf.lock
 */

int tty_prepare_flip_string_flags(struct tty_struct *tty,
			unsigned char **chars, char **flags, size_t size)
{
	int space = tty_buffer_request_room(tty, size);
	if (likely(space)) {
		struct tty_buffer *tb = tty->buf.tail;
		*chars = tb->char_buf_ptr + tb->used;
		*flags = tb->flag_buf_ptr + tb->used;
		tb->used += space;
	}
	return space;
}

EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);



/**
 *	tty_set_termios_ldisc		-	set ldisc field
 *	@tty: tty structure
 *	@num: line discipline number
 *
 *	This is probably overkill for real world processors but
 *	they are not on hot paths so a little discipline won't do
 *	any harm.
 *
 *	Locking: takes termios_mutex
 */

static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
{
	mutex_lock(&tty->termios_mutex);
	tty->termios->c_line = num;
	mutex_unlock(&tty->termios_mutex);
}

/*
 *	This guards the refcounted line discipline lists. The lock
 *	must be taken with irqs off because there are hangup path
 *	callers who will do ldisc lookups and cannot sleep.
 */

static DEFINE_SPINLOCK(tty_ldisc_lock);
static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
/* Line disc dispatch table */
static struct tty_ldisc tty_ldiscs[NR_LDISCS];

/**
 *	tty_register_ldisc	-	install a line discipline
 *	@disc: ldisc number
 *	@new_ldisc: pointer to the ldisc object
 *
 *	Installs a new line discipline into the kernel. The discipline
 *	is set up as unreferenced and then made available to the kernel
 *	from this point onwards.
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
	unsigned long flags;
	int ret = 0;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	tty_ldiscs[disc] = *new_ldisc;
	tty_ldiscs[disc].num = disc;
	tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
	tty_ldiscs[disc].refcount = 0;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	return ret;
}
EXPORT_SYMBOL(tty_register_ldisc);

/**
 *	tty_unregister_ldisc	-	unload a line discipline
 *	@disc: ldisc number
 *	@new_ldisc: pointer to the ldisc object
 *
 *	Remove a line discipline from the kernel providing it is not
 *	currently in use.
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

int tty_unregister_ldisc(int disc)
{
	unsigned long flags;
	int ret = 0;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (tty_ldiscs[disc].refcount)
		ret = -EBUSY;
	else
		tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	return ret;
}
EXPORT_SYMBOL(tty_unregister_ldisc);

/**
 *	tty_ldisc_get		-	take a reference to an ldisc
 *	@disc: ldisc number
 *
 *	Takes a reference to a line discipline. Deals with refcounts and
 *	module locking counts. Returns NULL if the discipline is not available.
 *	Returns a pointer to the discipline and bumps the ref count if it is
 *	available
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

struct tty_ldisc *tty_ldisc_get(int disc)
{
	unsigned long flags;
	struct tty_ldisc *ld;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return NULL;

	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ld = &tty_ldiscs[disc];
	/* Check the entry is defined */
	if (ld->flags & LDISC_FLAG_DEFINED) {
		/* If the module is being unloaded we can't use it */
		if (!try_module_get(ld->owner))
			ld = NULL;
		else /* lock it */
			ld->refcount++;
	} else
		ld = NULL;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ld;
}

EXPORT_SYMBOL_GPL(tty_ldisc_get);

/**
 *	tty_ldisc_put		-	drop ldisc reference
 *	@disc: ldisc number
 *
 *	Drop a reference to a line discipline. Manage refcounts and
 *	module usage counts
 *
 *	Locking:
 *		takes tty_ldisc_lock to guard against ldisc races
 */

void tty_ldisc_put(int disc)
{
	struct tty_ldisc *ld;
	unsigned long flags;

	BUG_ON(disc < N_TTY || disc >= NR_LDISCS);

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty_ldiscs[disc];
	BUG_ON(ld->refcount == 0);
	ld->refcount--;
	module_put(ld->owner);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}

EXPORT_SYMBOL_GPL(tty_ldisc_put);

/**
 *	tty_ldisc_assign	-	set ldisc on a tty
 *	@tty: tty to assign
 *	@ld: line discipline
 *
 *	Install an instance of a line discipline into a tty structure. The
 *	ldisc must have a reference count above zero to ensure it remains/
 *	The tty instance refcount starts at zero.
 *
 *	Locking:
 *		Caller must hold references
 */

static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
{
	tty->ldisc = *ld;
	tty->ldisc.refcount = 0;
}

/**
 *	tty_ldisc_try		-	internal helper
 *	@tty: the tty
 *
 *	Make a single attempt to grab and bump the refcount on
 *	the tty ldisc. Return 0 on failure or 1 on success. This is
 *	used to implement both the waiting and non waiting versions
 *	of tty_ldisc_ref
 *
 *	Locking: takes tty_ldisc_lock
 */

static int tty_ldisc_try(struct tty_struct *tty)
{
	unsigned long flags;
	struct tty_ldisc *ld;
	int ret = 0;

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty->ldisc;
	if (test_bit(TTY_LDISC, &tty->flags)) {
		ld->refcount++;
		ret = 1;
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ret;
}

/**
 *	tty_ldisc_ref_wait	-	wait for the tty ldisc
 *	@tty: tty device
 *
 *	Dereference the line discipline for the terminal and take a
 *	reference to it. If the line discipline is in flux then
 *	wait patiently until it changes.
 *
 *	Note: Must not be called from an IRQ/timer context. The caller
 *	must also be careful not to hold other locks that will deadlock
 *	against a discipline change, such as an existing ldisc reference
 *	(which we check for)
 *
 *	Locking: call functions take tty_ldisc_lock
 */

struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
	/* wait_event is a macro */
	wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
	if (tty->ldisc.refcount == 0)
		printk(KERN_ERR "tty_ldisc_ref_wait\n");
	return &tty->ldisc;
}

EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);

/**
 *	tty_ldisc_ref		-	get the tty ldisc
 *	@tty: tty device
 *
 *	Dereference the line discipline for the terminal and take a
 *	reference to it. If the line discipline is in flux then
 *	return NULL. Can be called from IRQ and timer functions.
 *
 *	Locking: called functions take tty_ldisc_lock
 */

struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
{
	if (tty_ldisc_try(tty))
		return &tty->ldisc;
	return NULL;
}

EXPORT_SYMBOL_GPL(tty_ldisc_ref);

/**
 *	tty_ldisc_deref		-	free a tty ldisc reference
 *	@ld: reference to free up
 *
 *	Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
 *	be called in IRQ context.
 *
 *	Locking: takes tty_ldisc_lock
 */

void tty_ldisc_deref(struct tty_ldisc *ld)
{
	unsigned long flags;

	BUG_ON(ld == NULL);

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (ld->refcount == 0)
		printk(KERN_ERR "tty_ldisc_deref: no references.\n");
	else
		ld->refcount--;
	if (ld->refcount == 0)
		wake_up(&tty_ldisc_wait);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}

EXPORT_SYMBOL_GPL(tty_ldisc_deref);

/**
 *	tty_ldisc_enable	-	allow ldisc use
 *	@tty: terminal to activate ldisc on
 *
 *	Set the TTY_LDISC flag when the line discipline can be called
 *	again. Do necessary wakeups for existing sleepers.
 *
 *	Note: nobody should set this bit except via this function. Clearing
 *	directly is allowed.
 */

static void tty_ldisc_enable(struct tty_struct *tty)
{
	set_bit(TTY_LDISC, &tty->flags);
	wake_up(&tty_ldisc_wait);
}

/**
 *	tty_set_ldisc		-	set line discipline
 *	@tty: the terminal to set
 *	@ldisc: the line discipline
 *
 *	Set the discipline of a tty line. Must be called from a process
 *	context.
 *
 *	Locking: takes tty_ldisc_lock.
 *		 called functions take termios_mutex
 */

static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int retval = 0;
	struct tty_ldisc o_ldisc;
	char buf[64];
	int work;
	unsigned long flags;
	struct tty_ldisc *ld;
	struct tty_struct *o_tty;

	if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
		return -EINVAL;

restart:

	ld = tty_ldisc_get(ldisc);
	/* Eduardo Blanco <ejbs@cs.cs.com.uy> */
	/* Cyrus Durgin <cider@speakeasy.org> */
	if (ld == NULL) {
		request_module("tty-ldisc-%d", ldisc);
		ld = tty_ldisc_get(ldisc);
	}
	if (ld == NULL)
		return -EINVAL;

	/*
	 *	Problem: What do we do if this blocks ?
	 */

	tty_wait_until_sent(tty, 0);

	if (tty->ldisc.num == ldisc) {
		tty_ldisc_put(ldisc);
		return 0;
	}

	/*
	 *	No more input please, we are switching. The new ldisc
	 *	will update this value in the ldisc open function
	 */

	tty->receive_room = 0;

	o_ldisc = tty->ldisc;
	o_tty = tty->link;

	/*
	 *	Make sure we don't change while someone holds a
	 *	reference to the line discipline. The TTY_LDISC bit
	 *	prevents anyone taking a reference once it is clear.
	 *	We need the lock to avoid racing reference takers.
	 */

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
		if (tty->ldisc.refcount) {
			/* Free the new ldisc we grabbed. Must drop the lock
			   first. */
			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
			tty_ldisc_put(ldisc);
			/*
			 * There are several reasons we may be busy, including
			 * random momentary I/O traffic. We must therefore
			 * retry. We could distinguish between blocking ops
			 * and retries if we made tty_ldisc_wait() smarter.
			 * That is up for discussion.
			 */
			if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
				return -ERESTARTSYS;
			goto restart;
		}
		if (o_tty && o_tty->ldisc.refcount) {
			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
			tty_ldisc_put(ldisc);
			if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
				return -ERESTARTSYS;
			goto restart;
		}
	}
	/*
	 *	If the TTY_LDISC bit is set, then we are racing against
	 *	another ldisc change
	 */
	if (!test_bit(TTY_LDISC, &tty->flags)) {
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		tty_ldisc_put(ldisc);
		ld = tty_ldisc_ref_wait(tty);
		tty_ldisc_deref(ld);
		goto restart;
	}

	clear_bit(TTY_LDISC, &tty->flags);
	if (o_tty)
		clear_bit(TTY_LDISC, &o_tty->flags);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	/*
	 *	From this point on we know nobody has an ldisc
	 *	usage reference, nor can they obtain one until
	 *	we say so later on.
	 */

	work = cancel_delayed_work(&tty->buf.work);
	/*
	 * Wait for ->hangup_work and ->buf.work handlers to terminate
	 */
	flush_scheduled_work();
	/* Shutdown the current discipline. */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);

	/* Now set up the new line discipline. */
	tty_ldisc_assign(tty, ld);
	tty_set_termios_ldisc(tty, ldisc);
	if (tty->ldisc.open)
		retval = (tty->ldisc.open)(tty);
	if (retval < 0) {
		tty_ldisc_put(ldisc);
		/* There is an outstanding reference here so this is safe */
		tty_ldisc_assign(tty, tty_ldisc_get(o_ldisc.num));
		tty_set_termios_ldisc(tty, tty->ldisc.num);
		if (tty->ldisc.open && (tty->ldisc.open(tty) < 0)) {
			tty_ldisc_put(o_ldisc.num);
			/* This driver is always present */
			tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
			tty_set_termios_ldisc(tty, N_TTY);
			if (tty->ldisc.open) {
				int r = tty->ldisc.open(tty);

				if (r < 0)
					panic("Couldn't open N_TTY ldisc for "
					      "%s --- error %d.",
					      tty_name(tty, buf), r);
			}
		}
	}
	/* At this point we hold a reference to the new ldisc and a
	   a reference to the old ldisc. If we ended up flipping back
	   to the existing ldisc we have two references to it */

	if (tty->ldisc.num != o_ldisc.num && tty->ops->set_ldisc)
		tty->ops->set_ldisc(tty);

	tty_ldisc_put(o_ldisc.num);

	/*
	 *	Allow ldisc referencing to occur as soon as the driver
	 *	ldisc callback completes.
	 */

	tty_ldisc_enable(tty);
	if (o_tty)
		tty_ldisc_enable(o_tty);

	/* Restart it in case no characters kick it off. Safe if
	   already running */
	if (work)
		schedule_delayed_work(&tty->buf.work, 1);
	return retval;
}

/**
 *	get_tty_driver		-	find device of a tty
 *	@dev_t: device identifier
 *	@index: returns the index of the tty
 *
 *	This routine returns a tty driver structure, given a device number
 *	and also passes back the index number.
 *
 *	Locking: caller must hold tty_mutex
 */

static struct tty_driver *get_tty_driver(dev_t device, int *index)
{
	struct tty_driver *p;

	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		dev_t base = MKDEV(p->major, p->minor_start);
		if (device < base || device >= base + p->num)
			continue;
		*index = device - base;
		return p;
	}
	return NULL;
}

#ifdef CONFIG_CONSOLE_POLL

/**
 *	tty_find_polling_driver	-	find device of a polled tty
 *	@name: name string to match
 *	@line: pointer to resulting tty line nr
 *
 *	This routine returns a tty driver structure, given a name
 *	and the condition that the tty driver is capable of polled
 *	operation.
 */
struct tty_driver *tty_find_polling_driver(char *name, int *line)
{
	struct tty_driver *p, *res = NULL;
	int tty_line = 0;
	char *str;

	mutex_lock(&tty_mutex);
	/* Search through the tty devices to look for a match */
	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		str = name + strlen(p->name);
		tty_line = simple_strtoul(str, &str, 10);
		if (*str == ',')
			str++;
		if (*str == '\0')
			str = NULL;

		if (tty_line >= 0 && tty_line <= p->num && p->ops &&
		    p->ops->poll_init && !p->ops->poll_init(p, tty_line, str)) {
			res = p;
			*line = tty_line;
			break;
		}
	}
	mutex_unlock(&tty_mutex);

	return res;
}
EXPORT_SYMBOL_GPL(tty_find_polling_driver);
#endif

/**
 *	tty_check_change	-	check for POSIX terminal changes
 *	@tty: tty to check
 *
 *	If we try to write to, or set the state of, a terminal and we're
 *	not in the foreground, send a SIGTTOU.  If the signal is blocked or
 *	ignored, go ahead and perform the operation.  (POSIX 7.2)
 *
 *	Locking: ctrl_lock
 */

int tty_check_change(struct tty_struct *tty)
{
	unsigned long flags;
	int ret = 0;

	if (current->signal->tty != tty)
		return 0;

	spin_lock_irqsave(&tty->ctrl_lock, flags);

	if (!tty->pgrp) {
		printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
		goto out;
	}
	if (task_pgrp(current) == tty->pgrp)
		goto out;
	if (is_ignored(SIGTTOU))
		goto out;
	if (is_current_pgrp_orphaned()) {
		ret = -EIO;
		goto out;
	}
	kill_pgrp(task_pgrp(current), SIGTTOU, 1);
	set_thread_flag(TIF_SIGPENDING);
	ret = -ERESTARTSYS;
out:
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	return ret;
}

EXPORT_SYMBOL(tty_check_change);

static ssize_t hung_up_tty_read(struct file *file, char __user *buf,
				size_t count, loff_t *ppos)
{
	return 0;
}

static ssize_t hung_up_tty_write(struct file *file, const char __user *buf,
				 size_t count, loff_t *ppos)
{
	return -EIO;
}

/* No kernel lock held - none needed ;) */
static unsigned int hung_up_tty_poll(struct file *filp, poll_table *wait)
{
	return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
}

static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
		unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}

static long hung_up_tty_compat_ioctl(struct file *file,
				     unsigned int cmd, unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}

static const struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

#ifdef CONFIG_UNIX98_PTYS
static const struct file_operations ptmx_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= ptmx_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};
#endif

static const struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.unlocked_ioctl	= tty_ioctl,
	.compat_ioctl	= tty_compat_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static const struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.unlocked_ioctl	= hung_up_tty_ioctl,
	.compat_ioctl	= hung_up_tty_compat_ioctl,
	.release	= tty_release,
};

static DEFINE_SPINLOCK(redirect_lock);
static struct file *redirect;

/**
 *	tty_wakeup	-	request more data
 *	@tty: terminal
 *
 *	Internal and external helper for wakeups of tty. This function
 *	informs the line discipline if present that the driver is ready
 *	to receive more output data.
 */

void tty_wakeup(struct tty_struct *tty)
{
	struct tty_ldisc *ld;

	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
		ld = tty_ldisc_ref(tty);
		if (ld) {
			if (ld->write_wakeup)
				ld->write_wakeup(tty);
			tty_ldisc_deref(ld);
		}
	}
	wake_up_interruptible(&tty->write_wait);
}

EXPORT_SYMBOL_GPL(tty_wakeup);

/**
 *	tty_ldisc_flush	-	flush line discipline queue
 *	@tty: tty
 *
 *	Flush the line discipline queue (if any) for this tty. If there
 *	is no line discipline active this is a no-op.
 */

void tty_ldisc_flush(struct tty_struct *tty)
{
	struct tty_ldisc *ld = tty_ldisc_ref(tty);
	if (ld) {
		if (ld->flush_buffer)
			ld->flush_buffer(tty);
		tty_ldisc_deref(ld);
	}
	tty_buffer_flush(tty);
}

EXPORT_SYMBOL_GPL(tty_ldisc_flush);

/**
 *	tty_reset_termios	-	reset terminal state
 *	@tty: tty to reset
 *
 *	Restore a terminal to the driver default state
 */

static void tty_reset_termios(struct tty_struct *tty)
{
	mutex_lock(&tty->termios_mutex);
	*tty->termios = tty->driver->init_termios;
	tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
	tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
	mutex_unlock(&tty->termios_mutex);
}

/**
 *	do_tty_hangup		-	actual handler for hangup events
 *	@work: tty device
 *
 *	This can be called by the "eventd" kernel thread.  That is process
 *	synchronous but doesn't hold any locks, so we need to make sure we
 *	have the appropriate locks for what we're doing.
 *
 *	The hangup event clears any pending redirections onto the hung up
 *	device. It ensures future writes will error and it does the needed
 *	line discipline hangup and signal delivery. The tty object itself
 *	remains intact.
 *
 *	Locking:
 *		BKL
 *		  redirect lock for undoing redirection
 *		  file list lock for manipulating list of ttys
 *		  tty_ldisc_lock from called functions
 *		  termios_mutex resetting termios data
 *		  tasklist_lock to walk task list for hangup event
 *		    ->siglock to protect ->signal/->sighand
 */
static void do_tty_hangup(struct work_struct *work)
{
	struct tty_struct *tty =
		container_of(work, struct tty_struct, hangup_work);
	struct file *cons_filp = NULL;
	struct file *filp, *f = NULL;
	struct task_struct *p;
	struct tty_ldisc *ld;
	int    closecount = 0, n;
	unsigned long flags;

	if (!tty)
		return;

	/* inuse_filps is protected by the single kernel lock */
	lock_kernel();

	spin_lock(&redirect_lock);
	if (redirect && redirect->private_data == tty) {
		f = redirect;
		redirect = NULL;
	}
	spin_unlock(&redirect_lock);

	check_tty_count(tty, "do_tty_hangup");
	file_list_lock();
	/* This breaks for file handles being sent over AF_UNIX sockets ? */
	list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
		if (filp->f_op->write == redirected_tty_write)
			cons_filp = filp;
		if (filp->f_op->write != tty_write)
			continue;
		closecount++;
		tty_fasync(-1, filp, 0);	/* can't block */
		filp->f_op = &hung_up_tty_fops;
	}
	file_list_unlock();
	/*
	 * FIXME! What are the locking issues here? This may me overdoing
	 * things... This question is especially important now that we've
	 * removed the irqlock.
	 */
	ld = tty_ldisc_ref(tty);
	if (ld != NULL) {
		/* We may have no line discipline at this point */
		if (ld->flush_buffer)
			ld->flush_buffer(tty);
		tty_driver_flush_buffer(tty);
		if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
		    ld->write_wakeup)
			ld->write_wakeup(tty);
		if (ld->hangup)
			ld->hangup(tty);
	}
	/*
	 * FIXME: Once we trust the LDISC code better we can wait here for
	 * ldisc completion and fix the driver call race
	 */
	wake_up_interruptible(&tty->write_wait);
	wake_up_interruptible(&tty->read_wait);
	/*
	 * Shutdown the current line discipline, and reset it to
	 * N_TTY.
	 */
	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
		tty_reset_termios(tty);
	/* Defer ldisc switch */
	/* tty_deferred_ldisc_switch(N_TTY);

	  This should get done automatically when the port closes and
	  tty_release is called */

	read_lock(&tasklist_lock);
	if (tty->session) {
		do_each_pid_task(tty->session, PIDTYPE_SID, p) {
			spin_lock_irq(&p->sighand->siglock);
			if (p->signal->tty == tty)
				p->signal->tty = NULL;
			if (!p->signal->leader) {
				spin_unlock_irq(&p->sighand->siglock);
				continue;
			}
			__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
			__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
			put_pid(p->signal->tty_old_pgrp);  /* A noop */
			spin_lock_irqsave(&tty->ctrl_lock, flags);
			if (tty->pgrp)
				p->signal->tty_old_pgrp = get_pid(tty->pgrp);
			spin_unlock_irqrestore(&tty->ctrl_lock, flags);
			spin_unlock_irq(&p->sighand->siglock);
		} while_each_pid_task(tty->session, PIDTYPE_SID, p);
	}
	read_unlock(&tasklist_lock);

	spin_lock_irqsave(&tty->ctrl_lock, flags);
	tty->flags = 0;
	put_pid(tty->session);
	put_pid(tty->pgrp);
	tty->session = NULL;
	tty->pgrp = NULL;
	tty->ctrl_status = 0;
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);

	/*
	 * If one of the devices matches a console pointer, we
	 * cannot just call hangup() because that will cause
	 * tty->count and state->count to go out of sync.
	 * So we just call close() the right number of times.
	 */
	if (cons_filp) {
		if (tty->ops->close)
			for (n = 0; n < closecount; n++)
				tty->ops->close(tty, cons_filp);
	} else if (tty->ops->hangup)
		(tty->ops->hangup)(tty);
	/*
	 * We don't want to have driver/ldisc interactions beyond
	 * the ones we did here. The driver layer expects no
	 * calls after ->hangup() from the ldisc side. However we
	 * can't yet guarantee all that.
	 */
	set_bit(TTY_HUPPED, &tty->flags);
	if (ld) {
		tty_ldisc_enable(tty);
		tty_ldisc_deref(ld);
	}
	unlock_kernel();
	if (f)
		fput(f);
}

/**
 *	tty_hangup		-	trigger a hangup event
 *	@tty: tty to hangup
 *
 *	A carrier loss (virtual or otherwise) has occurred on this like
 *	schedule a hangup sequence to run after this event.
 */

void tty_hangup(struct tty_struct *tty)
{
#ifdef TTY_DEBUG_HANGUP
	char	buf[64];
	printk(KERN_DEBUG "%s hangup...\n", tty_name(tty, buf));
#endif
	schedule_work(&tty->hangup_work);
}

EXPORT_SYMBOL(tty_hangup);

/**
 *	tty_vhangup		-	process vhangup
 *	@tty: tty to hangup
 *
 *	The user has asked via system call for the terminal to be hung up.
 *	We do this synchronously so that when the syscall returns the process
 *	is complete. That guarantee is necessary for security reasons.
 */

void tty_vhangup(struct tty_struct *tty)
{
#ifdef TTY_DEBUG_HANGUP
	char	buf[64];

	printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
#endif
	do_tty_hangup(&tty->hangup_work);
}

EXPORT_SYMBOL(tty_vhangup);

/**
 *	tty_hung_up_p		-	was tty hung up
 *	@filp: file pointer of tty
 *
 *	Return true if the tty has been subject to a vhangup or a carrier
 *	loss
 */

int tty_hung_up_p(struct file *filp)
{
	return (filp->f_op == &hung_up_tty_fops);
}

EXPORT_SYMBOL(tty_hung_up_p);

/**
 *	is_tty	-	checker whether file is a TTY
 *	@filp:		file handle that may be a tty
 *
 *	Check if the file handle is a tty handle.
 */

int is_tty(struct file *filp)
{
	return filp->f_op->read == tty_read
		|| filp->f_op->read == hung_up_tty_read;
}

static void session_clear_tty(struct pid *session)
{
	struct task_struct *p;
	do_each_pid_task(session, PIDTYPE_SID, p) {
		proc_clear_tty(p);
	} while_each_pid_task(session, PIDTYPE_SID, p);
}

/**
 *	disassociate_ctty	-	disconnect controlling tty
 *	@on_exit: true if exiting so need to "hang up" the session
 *
 *	This function is typically called only by the session leader, when
 *	it wants to disassociate itself from its controlling tty.
 *
 *	It performs the following functions:
 * 	(1)  Sends a SIGHUP and SIGCONT to the foreground process group
 * 	(2)  Clears the tty from being controlling the session
 * 	(3)  Clears the controlling tty for all processes in the
 * 		session group.
 *
 *	The argument on_exit is set to 1 if called when a process is
 *	exiting; it is 0 if called by the ioctl TIOCNOTTY.
 *
 *	Locking:
 *		BKL is taken for hysterical raisins
 *		  tty_mutex is taken to protect tty
 *		  ->siglock is taken to protect ->signal/->sighand
 *		  tasklist_lock is taken to walk process list for sessions
 *		    ->siglock is taken to protect ->signal/->sighand
 */

void disassociate_ctty(int on_exit)
{
	struct tty_struct *tty;
	struct pid *tty_pgrp = NULL;


	mutex_lock(&tty_mutex);
	tty = get_current_tty();
	if (tty) {
		tty_pgrp = get_pid(tty->pgrp);
		mutex_unlock(&tty_mutex);
		lock_kernel();
		/* XXX: here we race, there is nothing protecting tty */
		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
			tty_vhangup(tty);
		unlock_kernel();
	} else if (on_exit) {
		struct pid *old_pgrp;
		spin_lock_irq(&current->sighand->siglock);
		old_pgrp = current->signal->tty_old_pgrp;
		current->signal->tty_old_pgrp = NULL;
		spin_unlock_irq(&current->sighand->siglock);
		if (old_pgrp) {
			kill_pgrp(old_pgrp, SIGHUP, on_exit);
			kill_pgrp(old_pgrp, SIGCONT, on_exit);
			put_pid(old_pgrp);
		}
		mutex_unlock(&tty_mutex);
		return;
	}
	if (tty_pgrp) {
		kill_pgrp(tty_pgrp, SIGHUP, on_exit);
		if (!on_exit)
			kill_pgrp(tty_pgrp, SIGCONT, on_exit);
		put_pid(tty_pgrp);
	}

	spin_lock_irq(&current->sighand->siglock);
	put_pid(current->signal->tty_old_pgrp);
	current->signal->tty_old_pgrp = NULL;
	spin_unlock_irq(&current->sighand->siglock);

	mutex_lock(&tty_mutex);
	/* It is possible that do_tty_hangup has free'd this tty */
	tty = get_current_tty();
	if (tty) {
		unsigned long flags;
		spin_lock_irqsave(&tty->ctrl_lock, flags);
		put_pid(tty->session);
		put_pid(tty->pgrp);
		tty->session = NULL;
		tty->pgrp = NULL;
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	} else {
#ifdef TTY_DEBUG_HANGUP
		printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
		       " = NULL", tty);
#endif
	}
	mutex_unlock(&tty_mutex);

	/* Now clear signal->tty under the lock */
	read_lock(&tasklist_lock);
	session_clear_tty(task_session(current));
	read_unlock(&tasklist_lock);
}

/**
 *
 *	no_tty	- Ensure the current process does not have a controlling tty
 */
void no_tty(void)
{
	struct task_struct *tsk = current;
	lock_kernel();
	if (tsk->signal->leader)
		disassociate_ctty(0);
	unlock_kernel();
	proc_clear_tty(tsk);
}


/**
 *	stop_tty	-	propagate flow control
 *	@tty: tty to stop
 *
 *	Perform flow control to the driver. For PTY/TTY pairs we
 *	must also propagate the TIOCKPKT status. May be called
 *	on an already stopped device and will not re-call the driver
 *	method.
 *
 *	This functionality is used by both the line disciplines for
 *	halting incoming flow and by the driver. It may therefore be
 *	called from any context, may be under the tty atomic_write_lock
 *	but not always.
 *
 *	Locking:
 *		Uses the tty control lock internally
 */

void stop_tty(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->ctrl_lock, flags);
	if (tty->stopped) {
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
		return;
	}
	tty->stopped = 1;
	if (tty->link && tty->link->packet) {
		tty->ctrl_status &= ~TIOCPKT_START;
		tty->ctrl_status |= TIOCPKT_STOP;
		wake_up_interruptible(&tty->link->read_wait);
	}
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	if (tty->ops->stop)
		(tty->ops->stop)(tty);
}

EXPORT_SYMBOL(stop_tty);

/**
 *	start_tty	-	propagate flow control
 *	@tty: tty to start
 *
 *	Start a tty that has been stopped if at all possible. Perform
 *	any necessary wakeups and propagate the TIOCPKT status. If this
 *	is the tty was previous stopped and is being started then the
 *	driver start method is invoked and the line discipline woken.
 *
 *	Locking:
 *		ctrl_lock
 */

void start_tty(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->ctrl_lock, flags);
	if (!tty->stopped || tty->flow_stopped) {
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
		return;
	}
	tty->stopped = 0;
	if (tty->link && tty->link->packet) {
		tty->ctrl_status &= ~TIOCPKT_STOP;
		tty->ctrl_status |= TIOCPKT_START;
		wake_up_interruptible(&tty->link->read_wait);
	}
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
	if (tty->ops->start)
		(tty->ops->start)(tty);
	/* If we have a running line discipline it may need kicking */
	tty_wakeup(tty);
}

EXPORT_SYMBOL(start_tty);

/**
 *	tty_read	-	read method for tty device files
 *	@file: pointer to tty file
 *	@buf: user buffer
 *	@count: size of user buffer
 *	@ppos: unused
 *
 *	Perform the read system call function on this terminal device. Checks
 *	for hung up devices before calling the line discipline method.
 *
 *	Locking:
 *		Locks the line discipline internally while needed. Multiple
 *	read calls may be outstanding in parallel.
 */

static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
			loff_t *ppos)
{
	int i;
	struct tty_struct *tty;
	struct inode *inode;
	struct tty_ldisc *ld;

	tty = (struct tty_struct *)file->private_data;
	inode = file->f_path.dentry->d_inode;
	if (tty_paranoia_check(tty, inode, "tty_read"))
		return -EIO;
	if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
		return -EIO;

	/* We want to wait for the line discipline to sort out in this
	   situation */
	ld = tty_ldisc_ref_wait(tty);
	if (ld->read)
		i = (ld->read)(tty, file, buf, count);
	else
		i = -EIO;
	tty_ldisc_deref(ld);
	if (i > 0)
		inode->i_atime = current_fs_time(inode->i_sb);
	return i;
}

void tty_write_unlock(struct tty_struct *tty)
{
	mutex_unlock(&tty->atomic_write_lock);
	wake_up_interruptible(&tty->write_wait);
}

int tty_write_lock(struct tty_struct *tty, int ndelay)
{
	if (!mutex_trylock(&tty->atomic_write_lock)) {
		if (ndelay)
			return -EAGAIN;
		if (mutex_lock_interruptible(&tty->atomic_write_lock))
			return -ERESTARTSYS;
	}
	return 0;
}

/*
 * Split writes up in sane blocksizes to avoid
 * denial-of-service type attacks
 */
static inline ssize_t do_tty_write(
	ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
	struct tty_struct *tty,
	struct file *file,
	const char __user *buf,
	size_t count)
{
	ssize_t ret, written = 0;
	unsigned int chunk;

	ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
	if (ret < 0)
		return ret;

	/*
	 * We chunk up writes into a temporary buffer. This
	 * simplifies low-level drivers immensely, since they
	 * don't have locking issues and user mode accesses.
	 *
	 * But if TTY_NO_WRITE_SPLIT is set, we should use a
	 * big chunk-size..
	 *
	 * The default chunk-size is 2kB, because the NTTY
	 * layer has problems with bigger chunks. It will
	 * claim to be able to handle more characters than
	 * it actually does.
	 *
	 * FIXME: This can probably go away now except that 64K chunks
	 * are too likely to fail unless switched to vmalloc...
	 */
	chunk = 2048;
	if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
		chunk = 65536;
	if (count < chunk)
		chunk = count;

	/* write_buf/write_cnt is protected by the atomic_write_lock mutex */
	if (tty->write_cnt < chunk) {
		unsigned char *buf;

		if (chunk < 1024)
			chunk = 1024;

		buf = kmalloc(chunk, GFP_KERNEL);
		if (!buf) {
			ret = -ENOMEM;
			goto out;
		}
		kfree(tty->write_buf);
		tty->write_cnt = chunk;
		tty->write_buf = buf;
	}

	/* Do the write .. */
	for (;;) {
		size_t size = count;
		if (size > chunk)
			size = chunk;
		ret = -EFAULT;
		if (copy_from_user(tty->write_buf, buf, size))
			break;
		ret = write(tty, file, tty->write_buf, size);
		if (ret <= 0)
			break;
		written += ret;
		buf += ret;
		count -= ret;
		if (!count)
			break;
		ret = -ERESTARTSYS;
		if (signal_pending(current))
			break;
		cond_resched();
	}
	if (written) {
		struct inode *inode = file->f_path.dentry->d_inode;
		inode->i_mtime = current_fs_time(inode->i_sb);
		ret = written;
	}
out:
	tty_write_unlock(tty);
	return ret;
}


/**
 *	tty_write		-	write method for tty device file
 *	@file: tty file pointer
 *	@buf: user data to write
 *	@count: bytes to write
 *	@ppos: unused
 *
 *	Write data to a tty device via the line discipline.
 *
 *	Locking:
 *		Locks the line discipline as required
 *		Writes to the tty driver are serialized by the atomic_write_lock
 *	and are then processed in chunks to the device. The line discipline
 *	write method will not be involked in parallel for each device
 *		The line discipline write method is called under the big
 *	kernel lock for historical reasons. New code should not rely on this.
 */

static ssize_t tty_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	struct tty_struct *tty;
	struct inode *inode = file->f_path.dentry->d_inode;
	ssize_t ret;
	struct tty_ldisc *ld;

	tty = (struct tty_struct *)file->private_data;
	if (tty_paranoia_check(tty, inode, "tty_write"))
		return -EIO;
	if (!tty || !tty->ops->write ||
		(test_bit(TTY_IO_ERROR, &tty->flags)))
			return -EIO;
	/* Short term debug to catch buggy drivers */
	if (tty->ops->write_room == NULL)
		printk(KERN_ERR "tty driver %s lacks a write_room method.\n",
			tty->driver->name);
	ld = tty_ldisc_ref_wait(tty);
	if (!ld->write)
		ret = -EIO;
	else
		ret = do_tty_write(ld->write, tty, file, buf, count);
	tty_ldisc_deref(ld);
	return ret;
}

ssize_t redirected_tty_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	struct file *p = NULL;

	spin_lock(&redirect_lock);
	if (redirect) {
		get_file(redirect);
		p = redirect;
	}
	spin_unlock(&redirect_lock);

	if (p) {
		ssize_t res;
		res = vfs_write(p, buf, count, &p->f_pos);
		fput(p);
		return res;
	}
	return tty_write(file, buf, count, ppos);
}

static char ptychar[] = "pqrstuvwxyzabcde";

/**
 *	pty_line_name	-	generate name for a pty
 *	@driver: the tty driver in use
 *	@index: the minor number
 *	@p: output buffer of at least 6 bytes
 *
 *	Generate a name from a driver reference and write it to the output
 *	buffer.
 *
 *	Locking: None
 */
static void pty_line_name(struct tty_driver *driver, int index, char *p)
{
	int i = index + driver->name_base;
	/* ->name is initialized to "ttyp", but "tty" is expected */
	sprintf(p, "%s%c%x",
		driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
		ptychar[i >> 4 & 0xf], i & 0xf);
}

/**
 *	pty_line_name	-	generate name for a tty
 *	@driver: the tty driver in use
 *	@index: the minor number
 *	@p: output buffer of at least 7 bytes
 *
 *	Generate a name from a driver reference and write it to the output
 *	buffer.
 *
 *	Locking: None
 */
static void tty_line_name(struct tty_driver *driver, int index, char *p)
{
	sprintf(p, "%s%d", driver->name, index + driver->name_base);
}

/**
 *	init_dev		-	initialise a tty device
 *	@driver: tty driver we are opening a device on
 *	@idx: device index
 *	@tty: returned tty structure
 *
 *	Prepare a tty device. This may not be a "new" clean device but
 *	could also be an active device. The pty drivers require special
 *	handling because of this.
 *
 *	Locking:
 *		The function is called under the tty_mutex, which
 *	protects us from the tty struct or driver itself going away.
 *
 *	On exit the tty device has the line discipline attached and
 *	a reference count of 1. If a pair was created for pty/tty use
 *	and the other was a pty master then it too has a reference count of 1.
 *
 * WSH 06/09/97: Rewritten to remove races and properly clean up after a
 * failed open.  The new code protects the open with a mutex, so it's
 * really quite straightforward.  The mutex locking can probably be
 * relaxed for the (most common) case of reopening a tty.
 */

static int init_dev(struct tty_driver *driver, int idx,
	struct tty_struct **ret_tty)
{
	struct tty_struct *tty, *o_tty;
	struct ktermios *tp, **tp_loc, *o_tp, **o_tp_loc;
	struct ktermios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
	int retval = 0;

	/* check whether we're reopening an existing tty */
	if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
		tty = devpts_get_tty(idx);
		/*
		 * If we don't have a tty here on a slave open, it's because
		 * the master already started the close process and there's
		 * no relation between devpts file and tty anymore.
		 */
		if (!tty && driver->subtype == PTY_TYPE_SLAVE) {
			retval = -EIO;
			goto end_init;
		}
		/*
		 * It's safe from now on because init_dev() is called with
		 * tty_mutex held and release_dev() won't change tty->count
		 * or tty->flags without having to grab tty_mutex
		 */
		if (tty && driver->subtype == PTY_TYPE_MASTER)
			tty = tty->link;
	} else {
		tty = driver->ttys[idx];
	}
	if (tty) goto fast_track;

	/*
	 * First time open is complex, especially for PTY devices.
	 * This code guarantees that either everything succeeds and the
	 * TTY is ready for operation, or else the table slots are vacated
	 * and the allocated memory released.  (Except that the termios
	 * and locked termios may be retained.)
	 */

	if (!try_module_get(driver->owner)) {
		retval = -ENODEV;
		goto end_init;
	}

	o_tty = NULL;
	tp = o_tp = NULL;
	ltp = o_ltp = NULL;

	tty = alloc_tty_struct();
	if (!tty)
		goto fail_no_mem;
	initialize_tty_struct(tty);
	tty->driver = driver;
	tty->ops = driver->ops;
	tty->index = idx;
	tty_line_name(driver, idx, tty->name);

	if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
		tp_loc = &tty->termios;
		ltp_loc = &tty->termios_locked;
	} else {
		tp_loc = &driver->termios[idx];
		ltp_loc = &driver->termios_locked[idx];
	}

	if (!*tp_loc) {
		tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
		if (!tp)
			goto free_mem_out;
		*tp = driver->init_termios;
	}

	if (!*ltp_loc) {
		ltp = kzalloc(sizeof(struct ktermios), GFP_KERNEL);
		if (!ltp)
			goto free_mem_out;
	}

	if (driver->type == TTY_DRIVER_TYPE_PTY) {
		o_tty = alloc_tty_struct();
		if (!o_tty)
			goto free_mem_out;
		initialize_tty_struct(o_tty);
		o_tty->driver = driver->other;
		o_tty->ops = driver->ops;
		o_tty->index = idx;
		tty_line_name(driver->other, idx, o_tty->name);

		if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
			o_tp_loc = &o_tty->termios;
			o_ltp_loc = &o_tty->termios_locked;
		} else {
			o_tp_loc = &driver->other->termios[idx];
			o_ltp_loc = &driver->other->termios_locked[idx];
		}

		if (!*o_tp_loc) {
			o_tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
			if (!o_tp)
				goto free_mem_out;
			*o_tp = driver->other->init_termios;
		}

		if (!*o_ltp_loc) {
			o_ltp = kzalloc(sizeof(struct ktermios), GFP_KERNEL);
			if (!o_ltp)
				goto free_mem_out;
		}

		/*
		 * Everything allocated ... set up the o_tty structure.
		 */
		if (!(driver->other->flags & TTY_DRIVER_DEVPTS_MEM))
			driver->other->ttys[idx] = o_tty;
		if (!*o_tp_loc)
			*o_tp_loc = o_tp;
		if (!*o_ltp_loc)
			*o_ltp_loc = o_ltp;
		o_tty->termios = *o_tp_loc;
		o_tty->termios_locked = *o_ltp_loc;
		driver->other->refcount++;
		if (driver->subtype == PTY_TYPE_MASTER)
			o_tty->count++;

		/* Establish the links in both directions */
		tty->link   = o_tty;
		o_tty->link = tty;
	}

	/*
	 * All structures have been allocated, so now we install them.
	 * Failures after this point use release_tty to clean up, so
	 * there's no need to null out the local pointers.
	 */
	if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM))
		driver->ttys[idx] = tty;

	if (!*tp_loc)
		*tp_loc = tp;
	if (!*ltp_loc)
		*ltp_loc = ltp;
	tty->termios = *tp_loc;
	tty->termios_locked = *ltp_loc;
	/* Compatibility until drivers always set this */
	tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
	tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
	driver->refcount++;
	tty->count++;

	/*
	 * Structures all installed ... call the ldisc open routines.
	 * If we fail here just call release_tty to clean up.  No need
	 * to decrement the use counts, as release_tty doesn't care.
	 */

	if (tty->ldisc.open) {
		retval = (tty->ldisc.open)(tty);
		if (retval)
			goto release_mem_out;
	}
	if (o_tty && o_tty->ldisc.open) {
		retval = (o_tty->ldisc.open)(o_tty);
		if (retval) {
			if (tty->ldisc.close)
				(tty->ldisc.close)(tty);
			goto release_mem_out;
		}
		tty_ldisc_enable(o_tty);
	}
	tty_ldisc_enable(tty);
	goto success;

	/*
	 * This fast open can be used if the tty is already open.
	 * No memory is allocated, and the only failures are from
	 * attempting to open a closing tty or attempting multiple
	 * opens on a pty master.
	 */
fast_track:
	if (test_bit(TTY_CLOSING, &tty->flags)) {
		retval = -EIO;
		goto end_init;
	}
	if (driver->type == TTY_DRIVER_TYPE_PTY &&
	    driver->subtype == PTY_TYPE_MASTER) {
		/*
		 * special case for PTY masters: only one open permitted,
		 * and the slave side open count is incremented as well.
		 */
		if (tty->count) {
			retval = -EIO;
			goto end_init;
		}
		tty->link->count++;
	}
	tty->count++;
	tty->driver = driver; /* N.B. why do this every time?? */

	/* FIXME */
	if (!test_bit(TTY_LDISC, &tty->flags))
		printk(KERN_ERR "init_dev but no ldisc\n");
success:
	*ret_tty = tty;

	/* All paths come through here to release the mutex */
end_init:
	return retval;

	/* Release locally allocated memory ... nothing placed in slots */
free_mem_out:
	kfree(o_tp);
	if (o_tty)
		free_tty_struct(o_tty);
	kfree(ltp);
	kfree(tp);
	free_tty_struct(tty);

fail_no_mem:
	module_put(driver->owner);
	retval = -ENOMEM;
	goto end_init;

	/* call the tty release_tty routine to clean out this slot */
release_mem_out:
	if (printk_ratelimit())
		printk(KERN_INFO "init_dev: ldisc open failed, "
				 "clearing slot %d\n", idx);
	release_tty(tty, idx);
	goto end_init;
}

/**
 *	release_one_tty		-	release tty structure memory
 *
 *	Releases memory associated with a tty structure, and clears out the
 *	driver table slots. This function is called when a device is no longer
 *	in use. It also gets called when setup of a device fails.
 *
 *	Locking:
 *		tty_mutex - sometimes only
 *		takes the file list lock internally when working on the list
 *	of ttys that the driver keeps.
 *		FIXME: should we require tty_mutex is held here ??
 */
static void release_one_tty(struct tty_struct *tty, int idx)
{
	int devpts = tty->driver->flags & TTY_DRIVER_DEVPTS_MEM;
	struct ktermios *tp;

	if (!devpts)
		tty->driver->ttys[idx] = NULL;

	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
		tp = tty->termios;
		if (!devpts)
			tty->driver->termios[idx] = NULL;
		kfree(tp);

		tp = tty->termios_locked;
		if (!devpts)
			tty->driver->termios_locked[idx] = NULL;
		kfree(tp);
	}


	tty->magic = 0;
	tty->driver->refcount--;

	file_list_lock();
	list_del_init(&tty->tty_files);
	file_list_unlock();

	free_tty_struct(tty);
}

/**
 *	release_tty		-	release tty structure memory
 *
 *	Release both @tty and a possible linked partner (think pty pair),
 *	and decrement the refcount of the backing module.
 *
 *	Locking:
 *		tty_mutex - sometimes only
 *		takes the file list lock internally when working on the list
 *	of ttys that the driver keeps.
 *		FIXME: should we require tty_mutex is held here ??
 */
static void release_tty(struct tty_struct *tty, int idx)
{
	struct tty_driver *driver = tty->driver;

	if (tty->link)
		release_one_tty(tty->link, idx);
	release_one_tty(tty, idx);
	module_put(driver->owner);
}

/*
 * Even releasing the tty structures is a tricky business.. We have
 * to be very careful that the structures are all released at the
 * same time, as interrupts might otherwise get the wrong pointers.
 *
 * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
 * lead to double frees or releasing memory still in use.
 */
static void release_dev(struct file *filp)
{
	struct tty_struct *tty, *o_tty;
	int	pty_master, tty_closing, o_tty_closing, do_sleep;
	int	devpts;
	int	idx;
	char	buf[64];
	unsigned long flags;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode,
							"release_dev"))
		return;

	check_tty_count(tty, "release_dev");

	tty_fasync(-1, filp, 0);

	idx = tty->index;
	pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
		      tty->driver->subtype == PTY_TYPE_MASTER);
	devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
	o_tty = tty->link;

#ifdef TTY_PARANOIA_CHECK
	if (idx < 0 || idx >= tty->driver->num) {
		printk(KERN_DEBUG "release_dev: bad idx when trying to "
				  "free (%s)\n", tty->name);
		return;
	}
	if (!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
		if (tty != tty->driver->ttys[idx]) {
			printk(KERN_DEBUG "release_dev: driver.table[%d] not tty "
			       "for (%s)\n", idx, tty->name);
			return;
		}
		if (tty->termios != tty->driver->termios[idx]) {
			printk(KERN_DEBUG "release_dev: driver.termios[%d] not termios "
			       "for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (tty->termios_locked != tty->driver->termios_locked[idx]) {
			printk(KERN_DEBUG "release_dev: driver.termios_locked[%d] not "
			       "termios_locked for (%s)\n",
			       idx, tty->name);
			return;
		}
	}
#endif

#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "release_dev of %s (tty count=%d)...",
	       tty_name(tty, buf), tty->count);
#endif

#ifdef TTY_PARANOIA_CHECK
	if (tty->driver->other &&
	     !(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
		if (o_tty != tty->driver->other->ttys[idx]) {
			printk(KERN_DEBUG "release_dev: other->table[%d] "
					  "not o_tty for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (o_tty->termios != tty->driver->other->termios[idx]) {
			printk(KERN_DEBUG "release_dev: other->termios[%d] "
					  "not o_termios for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (o_tty->termios_locked !=
		      tty->driver->other->termios_locked[idx]) {
			printk(KERN_DEBUG "release_dev: other->termios_locked["
					  "%d] not o_termios_locked for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (o_tty->link != tty) {
			printk(KERN_DEBUG "release_dev: bad pty pointers\n");
			return;
		}
	}
#endif
	if (tty->ops->close)
		tty->ops->close(tty, filp);

	/*
	 * Sanity check: if tty->count is going to zero, there shouldn't be
	 * any waiters on tty->read_wait or tty->write_wait.  We test the
	 * wait queues and kick everyone out _before_ actually starting to
	 * close.  This ensures that we won't block while releasing the tty
	 * structure.
	 *
	 * The test for the o_tty closing is necessary, since the master and
	 * slave sides may close in any order.  If the slave side closes out
	 * first, its count will be one, since the master side holds an open.
	 * Thus this test wouldn't be triggered at the time the slave closes,
	 * so we do it now.
	 *
	 * Note that it's possible for the tty to be opened again while we're
	 * flushing out waiters.  By recalculating the closing flags before
	 * each iteration we avoid any problems.
	 */
	while (1) {
		/* Guard against races with tty->count changes elsewhere and
		   opens on /dev/tty */

		mutex_lock(&tty_mutex);
		tty_closing = tty->count <= 1;
		o_tty_closing = o_tty &&
			(o_tty->count <= (pty_master ? 1 : 0));
		do_sleep = 0;

		if (tty_closing) {
			if (waitqueue_active(&tty->read_wait)) {
				wake_up(&tty->read_wait);
				do_sleep++;
			}
			if (waitqueue_active(&tty->write_wait)) {
				wake_up(&tty->write_wait);
				do_sleep++;
			}
		}
		if (o_tty_closing) {
			if (waitqueue_active(&o_tty->read_wait)) {
				wake_up(&o_tty->read_wait);
				do_sleep++;
			}
			if (waitqueue_active(&o_tty->write_wait)) {
				wake_up(&o_tty->write_wait);
				do_sleep++;
			}
		}
		if (!do_sleep)
			break;

		printk(KERN_WARNING "release_dev: %s: read/write wait queue "
				    "active!\n", tty_name(tty, buf));
		mutex_unlock(&tty_mutex);
		schedule();
	}

	/*
	 * The closing flags are now consistent with the open counts on
	 * both sides, and we've completed the last operation that could
	 * block, so it's safe to proceed with closing.
	 */
	if (pty_master) {
		if (--o_tty->count < 0) {
			printk(KERN_WARNING "release_dev: bad pty slave count "
					    "(%d) for %s\n",
			       o_tty->count, tty_name(o_tty, buf));
			o_tty->count = 0;
		}
	}
	if (--tty->count < 0) {
		printk(KERN_WARNING "release_dev: bad tty->count (%d) for %s\n",
		       tty->count, tty_name(tty, buf));
		tty->count = 0;
	}

	/*
	 * We've decremented tty->count, so we need to remove this file
	 * descriptor off the tty->tty_files list; this serves two
	 * purposes:
	 *  - check_tty_count sees the correct number of file descriptors
	 *    associated with this tty.
	 *  - do_tty_hangup no longer sees this file descriptor as
	 *    something that needs to be handled for hangups.
	 */
	file_kill(filp);
	filp->private_data = NULL;

	/*
	 * Perform some housekeeping before deciding whether to return.
	 *
	 * Set the TTY_CLOSING flag if this was the last open.  In the
	 * case of a pty we may have to wait around for the other side
	 * to close, and TTY_CLOSING makes sure we can't be reopened.
	 */
	if (tty_closing)
		set_bit(TTY_CLOSING, &tty->flags);
	if (o_tty_closing)
		set_bit(TTY_CLOSING, &o_tty->flags);

	/*
	 * If _either_ side is closing, make sure there aren't any
	 * processes that still think tty or o_tty is their controlling
	 * tty.
	 */
	if (tty_closing || o_tty_closing) {
		read_lock(&tasklist_lock);
		session_clear_tty(tty->session);
		if (o_tty)
			session_clear_tty(o_tty->session);
		read_unlock(&tasklist_lock);
	}

	mutex_unlock(&tty_mutex);

	/* check whether both sides are closing ... */
	if (!tty_closing || (o_tty && !o_tty_closing))
		return;

#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "freeing tty structure...");
#endif
	/*
	 * Prevent flush_to_ldisc() from rescheduling the work for later.  Then
	 * kill any delayed work. As this is the final close it does not
	 * race with the set_ldisc code path.
	 */
	clear_bit(TTY_LDISC, &tty->flags);
	cancel_delayed_work(&tty->buf.work);

	/*
	 * Wait for ->hangup_work and ->buf.work handlers to terminate
	 */

	flush_scheduled_work();

	/*
	 * Wait for any short term users (we know they are just driver
	 * side waiters as the file is closing so user count on the file
	 * side is zero.
	 */
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	while (tty->ldisc.refcount) {
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
		spin_lock_irqsave(&tty_ldisc_lock, flags);
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	/*
	 * Shutdown the current line discipline, and reset it to N_TTY.
	 * N.B. why reset ldisc when we're releasing the memory??
	 *
	 * FIXME: this MUST get fixed for the new reflocking
	 */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);
	tty_ldisc_put(tty->ldisc.num);

	/*
	 *	Switch the line discipline back
	 */
	tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
	tty_set_termios_ldisc(tty, N_TTY);
	if (o_tty) {
		/* FIXME: could o_tty be in setldisc here ? */
		clear_bit(TTY_LDISC, &o_tty->flags);
		if (o_tty->ldisc.close)
			(o_tty->ldisc.close)(o_tty);
		tty_ldisc_put(o_tty->ldisc.num);
		tty_ldisc_assign(o_tty, tty_ldisc_get(N_TTY));
		tty_set_termios_ldisc(o_tty, N_TTY);
	}
	/*
	 * The release_tty function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	release_tty(tty, idx);

	/* Make this pty number available for reallocation */
	if (devpts)
		devpts_kill_index(idx);
}

/**
 *	tty_open		-	open a tty device
 *	@inode: inode of device file
 *	@filp: file pointer to tty
 *
 *	tty_open and tty_release keep up the tty count that contains the
 *	number of opens done on a tty. We cannot use the inode-count, as
 *	different inodes might point to the same tty.
 *
 *	Open-counting is needed for pty masters, as well as for keeping
 *	track of serial lines: DTR is dropped when the last close happens.
 *	(This is not done solely through tty->count, now.  - Ted 1/27/92)
 *
 *	The termios state of a pty is reset on first open so that
 *	settings don't persist across reuse.
 *
 *	Locking: tty_mutex protects tty, get_tty_driver and init_dev work.
 *		 tty->count should protect the rest.
 *		 ->siglock protects ->signal/->sighand
 */

static int tty_open(struct inode *inode, struct file *filp)
{
	struct tty_struct *tty;
	int noctty, retval;
	struct tty_driver *driver;
	int index;
	dev_t device = inode->i_rdev;
	unsigned short saved_flags = filp->f_flags;

	nonseekable_open(inode, filp);

retry_open:
	noctty = filp->f_flags & O_NOCTTY;
	index  = -1;
	retval = 0;

	mutex_lock(&tty_mutex);

	if (device == MKDEV(TTYAUX_MAJOR, 0)) {
		tty = get_current_tty();
		if (!tty) {
			mutex_unlock(&tty_mutex);
			return -ENXIO;
		}
		driver = tty->driver;
		index = tty->index;
		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
		/* noctty = 1; */
		goto got_driver;
	}
#ifdef CONFIG_VT
	if (device == MKDEV(TTY_MAJOR, 0)) {
		extern struct tty_driver *console_driver;
		driver = console_driver;
		index = fg_console;
		noctty = 1;
		goto got_driver;
	}
#endif
	if (device == MKDEV(TTYAUX_MAJOR, 1)) {
		driver = console_device(&index);
		if (driver) {
			/* Don't let /dev/console block */
			filp->f_flags |= O_NONBLOCK;
			noctty = 1;
			goto got_driver;
		}
		mutex_unlock(&tty_mutex);
		return -ENODEV;
	}

	driver = get_tty_driver(device, &index);
	if (!driver) {
		mutex_unlock(&tty_mutex);
		return -ENODEV;
	}
got_driver:
	retval = init_dev(driver, index, &tty);
	mutex_unlock(&tty_mutex);
	if (retval)
		return retval;

	filp->private_data = tty;
	file_move(filp, &tty->tty_files);
	check_tty_count(tty, "tty_open");
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		noctty = 1;
#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "opening %s...", tty->name);
#endif
	if (!retval) {
		if (tty->ops->open)
			retval = tty->ops->open(tty, filp);
		else
			retval = -ENODEV;
	}
	filp->f_flags = saved_flags;

	if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) &&
						!capable(CAP_SYS_ADMIN))
		retval = -EBUSY;

	if (retval) {
#ifdef TTY_DEBUG_HANGUP
		printk(KERN_DEBUG "error %d in opening %s...", retval,
		       tty->name);
#endif
		release_dev(filp);
		if (retval != -ERESTARTSYS)
			return retval;
		if (signal_pending(current))
			return retval;
		schedule();
		/*
		 * Need to reset f_op in case a hangup happened.
		 */
		if (filp->f_op == &hung_up_tty_fops)
			filp->f_op = &tty_fops;
		goto retry_open;
	}

	mutex_lock(&tty_mutex);
	spin_lock_irq(&current->sighand->siglock);
	if (!noctty &&
	    current->signal->leader &&
	    !current->signal->tty &&
	    tty->session == NULL)
		__proc_set_tty(current, tty);
	spin_unlock_irq(&current->sighand->siglock);
	mutex_unlock(&tty_mutex);
	return 0;
}

#ifdef CONFIG_UNIX98_PTYS
/**
 *	ptmx_open		-	open a unix 98 pty master
 *	@inode: inode of device file
 *	@filp: file pointer to tty
 *
 *	Allocate a unix98 pty master device from the ptmx driver.
 *
 *	Locking: tty_mutex protects theinit_dev work. tty->count should
 * 		protect the rest.
 *		allocated_ptys_lock handles the list of free pty numbers
 */

static int ptmx_open(struct inode *inode, struct file *filp)
{
	struct tty_struct *tty;
	int retval;
	int index;

	nonseekable_open(inode, filp);

	/* find a device that is not in use. */
	index = devpts_new_index();
	if (index < 0)
		return index;

	mutex_lock(&tty_mutex);
	retval = init_dev(ptm_driver, index, &tty);
	mutex_unlock(&tty_mutex);

	if (retval)
		goto out;

	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
	filp->private_data = tty;
	file_move(filp, &tty->tty_files);

	retval = devpts_pty_new(tty->link);
	if (retval)
		goto out1;

	check_tty_count(tty, "ptmx_open");
	retval = ptm_driver->ops->open(tty, filp);
	if (!retval)
		return 0;
out1:
	release_dev(filp);
	return retval;
out:
	devpts_kill_index(index);
	return retval;
}
#endif

/**
 *	tty_release		-	vfs callback for close
 *	@inode: inode of tty
 *	@filp: file pointer for handle to tty
 *
 *	Called the last time each file handle is closed that references
 *	this tty. There may however be several such references.
 *
 *	Locking:
 *		Takes bkl. See release_dev
 */

static int tty_release(struct inode *inode, struct file *filp)
{
	lock_kernel();
	release_dev(filp);
	unlock_kernel();
	return 0;
}

/**
 *	tty_poll	-	check tty status
 *	@filp: file being polled
 *	@wait: poll wait structures to update
 *
 *	Call the line discipline polling method to obtain the poll
 *	status of the device.
 *
 *	Locking: locks called line discipline but ldisc poll method
 *	may be re-entered freely by other callers.
 */

static unsigned int tty_poll(struct file *filp, poll_table *wait)
{
	struct tty_struct *tty;
	struct tty_ldisc *ld;
	int ret = 0;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_poll"))
		return 0;

	ld = tty_ldisc_ref_wait(tty);
	if (ld->poll)
		ret = (ld->poll)(tty, filp, wait);
	tty_ldisc_deref(ld);
	return ret;
}

static int tty_fasync(int fd, struct file *filp, int on)
{
	struct tty_struct *tty;
	unsigned long flags;
	int retval;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_fasync"))
		return 0;

	retval = fasync_helper(fd, filp, on, &tty->fasync);
	if (retval <= 0)
		return retval;

	if (on) {
		enum pid_type type;
		struct pid *pid;
		if (!waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = 1;
		spin_lock_irqsave(&tty->ctrl_lock, flags);
		if (tty->pgrp) {
			pid = tty->pgrp;
			type = PIDTYPE_PGID;
		} else {
			pid = task_pid(current);
			type = PIDTYPE_PID;
		}
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
		retval = __f_setown(filp, pid, type, 0);
		if (retval)
			return retval;
	} else {
		if (!tty->fasync && !waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = N_TTY_BUF_SIZE;
	}
	return 0;
}

/**
 *	tiocsti			-	fake input character
 *	@tty: tty to fake input into
 *	@p: pointer to character
 *
 *	Fake input to a tty device. Does the necessary locking and
 *	input management.
 *
 *	FIXME: does not honour flow control ??
 *
 *	Locking:
 *		Called functions take tty_ldisc_lock
 *		current->signal->tty check is safe without locks
 *
 *	FIXME: may race normal receive processing
 */

static int tiocsti(struct tty_struct *tty, char __user *p)
{
	char ch, mbz = 0;
	struct tty_ldisc *ld;

	if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (get_user(ch, p))
		return -EFAULT;
	ld = tty_ldisc_ref_wait(tty);
	ld->receive_buf(tty, &ch, &mbz, 1);
	tty_ldisc_deref(ld);
	return 0;
}

/**
 *	tiocgwinsz		-	implement window query ioctl
 *	@tty; tty
 *	@arg: user buffer for result
 *
 *	Copies the kernel idea of the window size into the user buffer.
 *
 *	Locking: tty->termios_mutex is taken to ensure the winsize data
 *		is consistent.
 */

static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
{
	int err;

	mutex_lock(&tty->termios_mutex);
	err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
	mutex_unlock(&tty->termios_mutex);

	return err ? -EFAULT: 0;
}

/**
 *	tiocswinsz		-	implement window size set ioctl
 *	@tty; tty
 *	@arg: user buffer for result
 *
 *	Copies the user idea of the window size to the kernel. Traditionally
 *	this is just advisory information but for the Linux console it
 *	actually has driver level meaning and triggers a VC resize.
 *
 *	Locking:
 *		Called function use the console_sem is used to ensure we do
 *	not try and resize the console twice at once.
 *		The tty->termios_mutex is used to ensure we don't double
 *	resize and get confused. Lock order - tty->termios_mutex before
 *	console sem
 */

static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
	struct winsize __user *arg)
{
	struct winsize tmp_ws;
	struct pid *pgrp, *rpgrp;
	unsigned long flags;

	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
		return -EFAULT;

	mutex_lock(&tty->termios_mutex);
	if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
		goto done;

#ifdef CONFIG_VT
	if (tty->driver->type == TTY_DRIVER_TYPE_CONSOLE) {
		if (vc_lock_resize(tty->driver_data, tmp_ws.ws_col,
					tmp_ws.ws_row)) {
			mutex_unlock(&tty->termios_mutex);
			return -ENXIO;
		}
	}
#endif
	/* Get the PID values and reference them so we can
	   avoid holding the tty ctrl lock while sending signals */
	spin_lock_irqsave(&tty->ctrl_lock, flags);
	pgrp = get_pid(tty->pgrp);
	rpgrp = get_pid(real_tty->pgrp);
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);

	if (pgrp)
		kill_pgrp(pgrp, SIGWINCH, 1);
	if (rpgrp != pgrp && rpgrp)
		kill_pgrp(rpgrp, SIGWINCH, 1);

	put_pid(pgrp);
	put_pid(rpgrp);

	tty->winsize = tmp_ws;
	real_tty->winsize = tmp_ws;
done:
	mutex_unlock(&tty->termios_mutex);
	return 0;
}

/**
 *	tioccons	-	allow admin to move logical console
 *	@file: the file to become console
 *
 *	Allow the adminstrator to move the redirected console device
 *
 *	Locking: uses redirect_lock to guard the redirect information
 */

static int tioccons(struct file *file)
{
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (file->f_op->write == redirected_tty_write) {
		struct file *f;
		spin_lock(&redirect_lock);
		f = redirect;
		redirect = NULL;
		spin_unlock(&redirect_lock);
		if (f)
			fput(f);
		return 0;
	}
	spin_lock(&redirect_lock);
	if (redirect) {
		spin_unlock(&redirect_lock);
		return -EBUSY;
	}
	get_file(file);
	redirect = file;
	spin_unlock(&redirect_lock);
	return 0;
}

/**
 *	fionbio		-	non blocking ioctl
 *	@file: file to set blocking value
 *	@p: user parameter
 *
 *	Historical tty interfaces had a blocking control ioctl before
 *	the generic functionality existed. This piece of history is preserved
 *	in the expected tty API of posix OS's.
 *
 *	Locking: none, the open fle handle ensures it won't go away.
 */

static int fionbio(struct file *file, int __user *p)
{
	int nonblock;

	if (get_user(nonblock, p))
		return -EFAULT;

	/* file->f_flags is still BKL protected in the fs layer - vomit */
	lock_kernel();
	if (nonblock)
		file->f_flags |= O_NONBLOCK;
	else
		file->f_flags &= ~O_NONBLOCK;
	unlock_kernel();
	return 0;
}

/**
 *	tiocsctty	-	set controlling tty
 *	@tty: tty structure
 *	@arg: user argument
 *
 *	This ioctl is used to manage job control. It permits a session
 *	leader to set this tty as the controlling tty for the session.
 *
 *	Locking:
 *		Takes tty_mutex() to protect tty instance
 *		Takes tasklist_lock internally to walk sessions
 *		Takes ->siglock() when updating signal->tty
 */

static int tiocsctty(struct tty_struct *tty, int arg)
{
	int ret = 0;
	if (current->signal->leader && (task_session(current) == tty->session))
		return ret;

	mutex_lock(&tty_mutex);
	/*
	 * The process must be a session leader and
	 * not have a controlling tty already.
	 */
	if (!current->signal->leader || current->signal->tty) {
		ret = -EPERM;
		goto unlock;
	}

	if (tty->session) {
		/*
		 * This tty is already the controlling
		 * tty for another session group!
		 */
		if (arg == 1 && capable(CAP_SYS_ADMIN)) {
			/*
			 * Steal it away
			 */
			read_lock(&tasklist_lock);
			session_clear_tty(tty->session);
			read_unlock(&tasklist_lock);
		} else {
			ret = -EPERM;
			goto unlock;
		}
	}
	proc_set_tty(current, tty);
unlock:
	mutex_unlock(&tty_mutex);
	return ret;
}

/**
 *	tty_get_pgrp	-	return a ref counted pgrp pid
 *	@tty: tty to read
 *
 *	Returns a refcounted instance of the pid struct for the process
 *	group controlling the tty.
 */

struct pid *tty_get_pgrp(struct tty_struct *tty)
{
	unsigned long flags;
	struct pid *pgrp;

	spin_lock_irqsave(&tty->ctrl_lock, flags);
	pgrp = get_pid(tty->pgrp);
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);

	return pgrp;
}
EXPORT_SYMBOL_GPL(tty_get_pgrp);

/**
 *	tiocgpgrp		-	get process group
 *	@tty: tty passed by user
 *	@real_tty: tty side of the tty pased by the user if a pty else the tty
 *	@p: returned pid
 *
 *	Obtain the process group of the tty. If there is no process group
 *	return an error.
 *
 *	Locking: none. Reference to current->signal->tty is safe.
 */

static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	struct pid *pid;
	int ret;
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	 */
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;
	pid = tty_get_pgrp(real_tty);
	ret =  put_user(pid_vnr(pid), p);
	put_pid(pid);
	return ret;
}

/**
 *	tiocspgrp		-	attempt to set process group
 *	@tty: tty passed by user
 *	@real_tty: tty side device matching tty passed by user
 *	@p: pid pointer
 *
 *	Set the process group of the tty to the session passed. Only
 *	permitted where the tty session is our session.
 *
 *	Locking: RCU, ctrl lock
 */

static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	struct pid *pgrp;
	pid_t pgrp_nr;
	int retval = tty_check_change(real_tty);
	unsigned long flags;

	if (retval == -EIO)
		return -ENOTTY;
	if (retval)
		return retval;
	if (!current->signal->tty ||
	    (current->signal->tty != real_tty) ||
	    (real_tty->session != task_session(current)))
		return -ENOTTY;
	if (get_user(pgrp_nr, p))
		return -EFAULT;
	if (pgrp_nr < 0)
		return -EINVAL;
	rcu_read_lock();
	pgrp = find_vpid(pgrp_nr);
	retval = -ESRCH;
	if (!pgrp)
		goto out_unlock;
	retval = -EPERM;
	if (session_of_pgrp(pgrp) != task_session(current))
		goto out_unlock;
	retval = 0;
	spin_lock_irqsave(&tty->ctrl_lock, flags);
	put_pid(real_tty->pgrp);
	real_tty->pgrp = get_pid(pgrp);
	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
out_unlock:
	rcu_read_unlock();
	return retval;
}

/**
 *	tiocgsid		-	get session id
 *	@tty: tty passed by user
 *	@real_tty: tty side of the tty pased by the user if a pty else the tty
 *	@p: pointer to returned session id
 *
 *	Obtain the session id of the tty. If there is no session
 *	return an error.
 *
 *	Locking: none. Reference to current->signal->tty is safe.
 */

static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	*/
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;
	if (!real_tty->session)
		return -ENOTTY;
	return put_user(pid_vnr(real_tty->session), p);
}

/**
 *	tiocsetd	-	set line discipline
 *	@tty: tty device
 *	@p: pointer to user data
 *
 *	Set the line discipline according to user request.
 *
 *	Locking: see tty_set_ldisc, this function is just a helper
 */

static int tiocsetd(struct tty_struct *tty, int __user *p)
{
	int ldisc;
	int ret;

	if (get_user(ldisc, p))
		return -EFAULT;

	lock_kernel();
	ret = tty_set_ldisc(tty, ldisc);
	unlock_kernel();

	return ret;
}

/**
 *	send_break	-	performed time break
 *	@tty: device to break on
 *	@duration: timeout in mS
 *
 *	Perform a timed break on hardware that lacks its own driver level
 *	timed break functionality.
 *
 *	Locking:
 *		atomic_write_lock serializes
 *
 */

static int send_break(struct tty_struct *tty, unsigned int duration)
{
	if (tty_write_lock(tty, 0) < 0)
		return -EINTR;
	tty->ops->break_ctl(tty, -1);
	if (!signal_pending(current))
		msleep_interruptible(duration);
	tty->ops->break_ctl(tty, 0);
	tty_write_unlock(tty);
	if (!signal_pending(current))
		return -EINTR;
	return 0;
}

/**
 *	tty_tiocmget		-	get modem status
 *	@tty: tty device
 *	@file: user file pointer
 *	@p: pointer to result
 *
 *	Obtain the modem status bits from the tty driver if the feature
 *	is supported. Return -EINVAL if it is not available.
 *
 *	Locking: none (up to the driver)
 */

static int tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p)
{
	int retval = -EINVAL;

	if (tty->ops->tiocmget) {
		retval = tty->ops->tiocmget(tty, file);

		if (retval >= 0)
			retval = put_user(retval, p);
	}
	return retval;
}

/**
 *	tty_tiocmset		-	set modem status
 *	@tty: tty device
 *	@file: user file pointer
 *	@cmd: command - clear bits, set bits or set all
 *	@p: pointer to desired bits
 *
 *	Set the modem status bits from the tty driver if the feature
 *	is supported. Return -EINVAL if it is not available.
 *
 *	Locking: none (up to the driver)
 */

static int tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int cmd,
	     unsigned __user *p)
{
	int retval = -EINVAL;

	if (tty->ops->tiocmset) {
		unsigned int set, clear, val;

		retval = get_user(val, p);
		if (retval)
			return retval;

		set = clear = 0;
		switch (cmd) {
		case TIOCMBIS:
			set = val;
			break;
		case TIOCMBIC:
			clear = val;
			break;
		case TIOCMSET:
			set = val;
			clear = ~val;
			break;
		}

		set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
		clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;

		retval = tty->ops->tiocmset(tty, file, set, clear);
	}
	return retval;
}

/*
 * Split this up, as gcc can choke on it otherwise..
 */
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct tty_struct *tty, *real_tty;
	void __user *p = (void __user *)arg;
	int retval;
	struct tty_ldisc *ld;
	struct inode *inode = file->f_dentry->d_inode;

	tty = (struct tty_struct *)file->private_data;
	if (tty_paranoia_check(tty, inode, "tty_ioctl"))
		return -EINVAL;

	real_tty = tty;
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		real_tty = tty->link;

	/*
	 * Break handling by driver
	 */

	retval = -EINVAL;

	if (!tty->ops->break_ctl) {
		switch (cmd) {
		case TIOCSBRK:
		case TIOCCBRK:
			if (tty->ops->ioctl)
				retval = tty->ops->ioctl(tty, file, cmd, arg);
			if (retval != -EINVAL && retval != -ENOIOCTLCMD)
				printk(KERN_WARNING "tty: driver %s needs updating to use break_ctl\n", tty->driver->name);
			return retval;

		/* These two ioctl's always return success; even if */
		/* the driver doesn't support them. */
		case TCSBRK:
		case TCSBRKP:
			if (!tty->ops->ioctl)
				return 0;
			retval = tty->ops->ioctl(tty, file, cmd, arg);
			if (retval != -EINVAL && retval != -ENOIOCTLCMD)
				printk(KERN_WARNING "tty: driver %s needs updating to use break_ctl\n", tty->driver->name);
			if (retval == -ENOIOCTLCMD)
				retval = 0;
			return retval;
		}
	}

	/*
	 * Factor out some common prep work
	 */
	switch (cmd) {
	case TIOCSETD:
	case TIOCSBRK:
	case TIOCCBRK:
	case TCSBRK:
	case TCSBRKP:
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		if (cmd != TIOCCBRK) {
			tty_wait_until_sent(tty, 0);
			if (signal_pending(current))
				return -EINTR;
		}
		break;
	}

	switch (cmd) {
	case TIOCSTI:
		return tiocsti(tty, p);
	case TIOCGWINSZ:
		return tiocgwinsz(tty, p);
	case TIOCSWINSZ:
		return tiocswinsz(tty, real_tty, p);
	case TIOCCONS:
		return real_tty != tty ? -EINVAL : tioccons(file);
	case FIONBIO:
		return fionbio(file, p);
	case TIOCEXCL:
		set_bit(TTY_EXCLUSIVE, &tty->flags);
		return 0;
	case TIOCNXCL:
		clear_bit(TTY_EXCLUSIVE, &tty->flags);
		return 0;
	case TIOCNOTTY:
		if (current->signal->tty != tty)
			return -ENOTTY;
		no_tty();
		return 0;
	case TIOCSCTTY:
		return tiocsctty(tty, arg);
	case TIOCGPGRP:
		return tiocgpgrp(tty, real_tty, p);
	case TIOCSPGRP:
		return tiocspgrp(tty, real_tty, p);
	case TIOCGSID:
		return tiocgsid(tty, real_tty, p);
	case TIOCGETD:
		return put_user(tty->ldisc.num, (int __user *)p);
	case TIOCSETD:
		return tiocsetd(tty, p);
#ifdef CONFIG_VT
	case TIOCLINUX:
		return tioclinux(tty, arg);
#endif
	/*
	 * Break handling
	 */
	case TIOCSBRK:	/* Turn break on, unconditionally */
		if (tty->ops->break_ctl)
			tty->ops->break_ctl(tty, -1);
		return 0;

	case TIOCCBRK:	/* Turn break off, unconditionally */
		if (tty->ops->break_ctl)
			tty->ops->break_ctl(tty, 0);
		return 0;
	case TCSBRK:   /* SVID version: non-zero arg --> no break */
		/* non-zero arg means wait for all output data
		 * to be sent (performed above) but don't send break.
		 * This is used by the tcdrain() termios function.
		 */
		if (!arg)
			return send_break(tty, 250);
		return 0;
	case TCSBRKP:	/* support for POSIX tcsendbreak() */
		return send_break(tty, arg ? arg*100 : 250);

	case TIOCMGET:
		return tty_tiocmget(tty, file, p);
	case TIOCMSET:
	case TIOCMBIC:
	case TIOCMBIS:
		return tty_tiocmset(tty, file, cmd, p);
	case TCFLSH:
		switch (arg) {
		case TCIFLUSH:
		case TCIOFLUSH:
		/* flush tty buffer and allow ldisc to process ioctl */
			tty_buffer_flush(tty);
			break;
		}
		break;
	}
	if (tty->ops->ioctl) {
		retval = (tty->ops->ioctl)(tty, file, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}
	ld = tty_ldisc_ref_wait(tty);
	retval = -EINVAL;
	if (ld->ioctl) {
		retval = ld->ioctl(tty, file, cmd, arg);
		if (retval == -ENOIOCTLCMD)
			retval = -EINVAL;
	}
	tty_ldisc_deref(ld);
	return retval;
}

#ifdef CONFIG_COMPAT
static long tty_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg)
{
	struct inode *inode = file->f_dentry->d_inode;
	struct tty_struct *tty = file->private_data;
	struct tty_ldisc *ld;
	int retval = -ENOIOCTLCMD;

	if (tty_paranoia_check(tty, inode, "tty_ioctl"))
		return -EINVAL;

	if (tty->ops->compat_ioctl) {
		retval = (tty->ops->compat_ioctl)(tty, file, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}

	ld = tty_ldisc_ref_wait(tty);
	if (ld->compat_ioctl)
		retval = ld->compat_ioctl(tty, file, cmd, arg);
	tty_ldisc_deref(ld);

	return retval;
}
#endif

/*
 * This implements the "Secure Attention Key" ---  the idea is to
 * prevent trojan horses by killing all processes associated with this
 * tty when the user hits the "Secure Attention Key".  Required for
 * super-paranoid applications --- see the Orange Book for more details.
 *
 * This code could be nicer; ideally it should send a HUP, wait a few
 * seconds, then send a INT, and then a KILL signal.  But you then
 * have to coordinate with the init process, since all processes associated
 * with the current tty must be dead before the new getty is allowed
 * to spawn.
 *
 * Now, if it would be correct ;-/ The current code has a nasty hole -
 * it doesn't catch files in flight. We may send the descriptor to ourselves
 * via AF_UNIX socket, close it and later fetch from socket. FIXME.
 *
 * Nasty bug: do_SAK is being called in interrupt context.  This can
 * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
 */
void __do_SAK(struct tty_struct *tty)
{
#ifdef TTY_SOFT_SAK
	tty_hangup(tty);
#else
	struct task_struct *g, *p;
	struct pid *session;
	int		i;
	struct file	*filp;
	struct fdtable *fdt;

	if (!tty)
		return;
	session = tty->session;

	tty_ldisc_flush(tty);

	tty_driver_flush_buffer(tty);

	read_lock(&tasklist_lock);
	/* Kill the entire session */
	do_each_pid_task(session, PIDTYPE_SID, p) {
		printk(KERN_NOTICE "SAK: killed process %d"
			" (%s): task_session_nr(p)==tty->session\n",
			task_pid_nr(p), p->comm);
		send_sig(SIGKILL, p, 1);
	} while_each_pid_task(session, PIDTYPE_SID, p);
	/* Now kill any processes that happen to have the
	 * tty open.
	 */
	do_each_thread(g, p) {
		if (p->signal->tty == tty) {
			printk(KERN_NOTICE "SAK: killed process %d"
			    " (%s): task_session_nr(p)==tty->session\n",
			    task_pid_nr(p), p->comm);
			send_sig(SIGKILL, p, 1);
			continue;
		}
		task_lock(p);
		if (p->files) {
			/*
			 * We don't take a ref to the file, so we must
			 * hold ->file_lock instead.
			 */
			spin_lock(&p->files->file_lock);
			fdt = files_fdtable(p->files);
			for (i = 0; i < fdt->max_fds; i++) {
				filp = fcheck_files(p->files, i);
				if (!filp)
					continue;
				if (filp->f_op->read == tty_read &&
				    filp->private_data == tty) {
					printk(KERN_NOTICE "SAK: killed process %d"
					    " (%s): fd#%d opened to the tty\n",
					    task_pid_nr(p), p->comm, i);
					force_sig(SIGKILL, p);
					break;
				}
			}
			spin_unlock(&p->files->file_lock);
		}
		task_unlock(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);
#endif
}

static void do_SAK_work(struct work_struct *work)
{
	struct tty_struct *tty =
		container_of(work, struct tty_struct, SAK_work);
	__do_SAK(tty);
}

/*
 * The tq handling here is a little racy - tty->SAK_work may already be queued.
 * Fortunately we don't need to worry, because if ->SAK_work is already queued,
 * the values which we write to it will be identical to the values which it
 * already has. --akpm
 */
void do_SAK(struct tty_struct *tty)
{
	if (!tty)
		return;
	schedule_work(&tty->SAK_work);
}

EXPORT_SYMBOL(do_SAK);

/**
 *	flush_to_ldisc
 *	@work: tty structure passed from work queue.
 *
 *	This routine is called out of the software interrupt to flush data
 *	from the buffer chain to the line discipline.
 *
 *	Locking: holds tty->buf.lock to guard buffer list. Drops the lock
 *	while invoking the line discipline receive_buf method. The
 *	receive_buf method is single threaded for each tty instance.
 */

static void flush_to_ldisc(struct work_struct *work)
{
	struct tty_struct *tty =
		container_of(work, struct tty_struct, buf.work.work);
	unsigned long 	flags;
	struct tty_ldisc *disc;
	struct tty_buffer *tbuf, *head;
	char *char_buf;
	unsigned char *flag_buf;

	disc = tty_ldisc_ref(tty);
	if (disc == NULL)	/*  !TTY_LDISC */
		return;

	spin_lock_irqsave(&tty->buf.lock, flags);
	/* So we know a flush is running */
	set_bit(TTY_FLUSHING, &tty->flags);
	head = tty->buf.head;
	if (head != NULL) {
		tty->buf.head = NULL;
		for (;;) {
			int count = head->commit - head->read;
			if (!count) {
				if (head->next == NULL)
					break;
				tbuf = head;
				head = head->next;
				tty_buffer_free(tty, tbuf);
				continue;
			}
			/* Ldisc or user is trying to flush the buffers
			   we are feeding to the ldisc, stop feeding the
			   line discipline as we want to empty the queue */
			if (test_bit(TTY_FLUSHPENDING, &tty->flags))
				break;
			if (!tty->receive_room) {
				schedule_delayed_work(&tty->buf.work, 1);
				break;
			}
			if (count > tty->receive_room)
				count = tty->receive_room;
			char_buf = head->char_buf_ptr + head->read;
			flag_buf = head->flag_buf_ptr + head->read;
			head->read += count;
			spin_unlock_irqrestore(&tty->buf.lock, flags);
			disc->receive_buf(tty, char_buf, flag_buf, count);
			spin_lock_irqsave(&tty->buf.lock, flags);
		}
		/* Restore the queue head */
		tty->buf.head = head;
	}
	/* We may have a deferred request to flush the input buffer,
	   if so pull the chain under the lock and empty the queue */
	if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
		__tty_buffer_flush(tty);
		clear_bit(TTY_FLUSHPENDING, &tty->flags);
		wake_up(&tty->read_wait);
	}
	clear_bit(TTY_FLUSHING, &tty->flags);
	spin_unlock_irqrestore(&tty->buf.lock, flags);

	tty_ldisc_deref(disc);
}

/**
 *	tty_flip_buffer_push	-	terminal
 *	@tty: tty to push
 *
 *	Queue a push of the terminal flip buffers to the line discipline. This
 *	function must not be called from IRQ context if tty->low_latency is set.
 *
 *	In the event of the queue being busy for flipping the work will be
 *	held off and retried later.
 *
 *	Locking: tty buffer lock. Driver locks in low latency mode.
 */

void tty_flip_buffer_push(struct tty_struct *tty)
{
	unsigned long flags;
	spin_lock_irqsave(&tty->buf.lock, flags);
	if (tty->buf.tail != NULL)
		tty->buf.tail->commit = tty->buf.tail->used;
	spin_unlock_irqrestore(&tty->buf.lock, flags);

	if (tty->low_latency)
		flush_to_ldisc(&tty->buf.work.work);
	else
		schedule_delayed_work(&tty->buf.work, 1);
}

EXPORT_SYMBOL(tty_flip_buffer_push);


/**
 *	initialize_tty_struct
 *	@tty: tty to initialize
 *
 *	This subroutine initializes a tty structure that has been newly
 *	allocated.
 *
 *	Locking: none - tty in question must not be exposed at this point
 */

static void initialize_tty_struct(struct tty_struct *tty)
{
	memset(tty, 0, sizeof(struct tty_struct));
	tty->magic = TTY_MAGIC;
	tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
	tty->session = NULL;
	tty->pgrp = NULL;
	tty->overrun_time = jiffies;
	tty->buf.head = tty->buf.tail = NULL;
	tty_buffer_init(tty);
	INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
	mutex_init(&tty->termios_mutex);
	init_waitqueue_head(&tty->write_wait);
	init_waitqueue_head(&tty->read_wait);
	INIT_WORK(&tty->hangup_work, do_tty_hangup);
	mutex_init(&tty->atomic_read_lock);
	mutex_init(&tty->atomic_write_lock);
	spin_lock_init(&tty->read_lock);
	spin_lock_init(&tty->ctrl_lock);
	INIT_LIST_HEAD(&tty->tty_files);
	INIT_WORK(&tty->SAK_work, do_SAK_work);
}

/**
 *	tty_put_char	-	write one character to a tty
 *	@tty: tty
 *	@ch: character
 *
 *	Write one byte to the tty using the provided put_char method
 *	if present. Returns the number of characters successfully output.
 *
 *	Note: the specific put_char operation in the driver layer may go
 *	away soon. Don't call it directly, use this method
 */

int tty_put_char(struct tty_struct *tty, unsigned char ch)
{
	if (tty->ops->put_char)
		return tty->ops->put_char(tty, ch);
	return tty->ops->write(tty, &ch, 1);
}

EXPORT_SYMBOL_GPL(tty_put_char);

static struct class *tty_class;

/**
 *	tty_register_device - register a tty device
 *	@driver: the tty driver that describes the tty device
 *	@index: the index in the tty driver for this tty device
 *	@device: a struct device that is associated with this tty device.
 *		This field is optional, if there is no known struct device
 *		for this tty device it can be set to NULL safely.
 *
 *	Returns a pointer to the struct device for this tty device
 *	(or ERR_PTR(-EFOO) on error).
 *
 *	This call is required to be made to register an individual tty device
 *	if the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set.  If
 *	that bit is not set, this function should not be called by a tty
 *	driver.
 *
 *	Locking: ??
 */

struct device *tty_register_device(struct tty_driver *driver, unsigned index,
				   struct device *device)
{
	char name[64];
	dev_t dev = MKDEV(driver->major, driver->minor_start) + index;

	if (index >= driver->num) {
		printk(KERN_ERR "Attempt to register invalid tty line number "
		       " (%d).\n", index);
		return ERR_PTR(-EINVAL);
	}

	if (driver->type == TTY_DRIVER_TYPE_PTY)
		pty_line_name(driver, index, name);
	else
		tty_line_name(driver, index, name);

	return device_create(tty_class, device, dev, name);
}

/**
 * 	tty_unregister_device - unregister a tty device
 * 	@driver: the tty driver that describes the tty device
 * 	@index: the index in the tty driver for this tty device
 *
 * 	If a tty device is registered with a call to tty_register_device() then
 *	this function must be called when the tty device is gone.
 *
 *	Locking: ??
 */

void tty_unregister_device(struct tty_driver *driver, unsigned index)
{
	device_destroy(tty_class,
		MKDEV(driver->major, driver->minor_start) + index);
}

EXPORT_SYMBOL(tty_register_device);
EXPORT_SYMBOL(tty_unregister_device);

struct tty_driver *alloc_tty_driver(int lines)
{
	struct tty_driver *driver;

	driver = kzalloc(sizeof(struct tty_driver), GFP_KERNEL);
	if (driver) {
		driver->magic = TTY_DRIVER_MAGIC;
		driver->num = lines;
		/* later we'll move allocation of tables here */
	}
	return driver;
}

void put_tty_driver(struct tty_driver *driver)
{
	kfree(driver);
}

void tty_set_operations(struct tty_driver *driver,
			const struct tty_operations *op)
{
	driver->ops = op;
};

EXPORT_SYMBOL(alloc_tty_driver);
EXPORT_SYMBOL(put_tty_driver);
EXPORT_SYMBOL(tty_set_operations);

/*
 * Called by a tty driver to register itself.
 */
int tty_register_driver(struct tty_driver *driver)
{
	int error;
	int i;
	dev_t dev;
	void **p = NULL;

	if (driver->flags & TTY_DRIVER_INSTALLED)
		return 0;

	if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM) && driver->num) {
		p = kzalloc(driver->num * 3 * sizeof(void *), GFP_KERNEL);
		if (!p)
			return -ENOMEM;
	}

	if (!driver->major) {
		error = alloc_chrdev_region(&dev, driver->minor_start,
						driver->num, driver->name);
		if (!error) {
			driver->major = MAJOR(dev);
			driver->minor_start = MINOR(dev);
		}
	} else {
		dev = MKDEV(driver->major, driver->minor_start);
		error = register_chrdev_region(dev, driver->num, driver->name);
	}
	if (error < 0) {
		kfree(p);
		return error;
	}

	if (p) {
		driver->ttys = (struct tty_struct **)p;
		driver->termios = (struct ktermios **)(p + driver->num);
		driver->termios_locked = (struct ktermios **)
							(p + driver->num * 2);
	} else {
		driver->ttys = NULL;
		driver->termios = NULL;
		driver->termios_locked = NULL;
	}

	cdev_init(&driver->cdev, &tty_fops);
	driver->cdev.owner = driver->owner;
	error = cdev_add(&driver->cdev, dev, driver->num);
	if (error) {
		unregister_chrdev_region(dev, driver->num);
		driver->ttys = NULL;
		driver->termios = driver->termios_locked = NULL;
		kfree(p);
		return error;
	}

	mutex_lock(&tty_mutex);
	list_add(&driver->tty_drivers, &tty_drivers);
	mutex_unlock(&tty_mutex);

	if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {
		for (i = 0; i < driver->num; i++)
		    tty_register_device(driver, i, NULL);
	}
	proc_tty_register_driver(driver);
	return 0;
}

EXPORT_SYMBOL(tty_register_driver);

/*
 * Called by a tty driver to unregister itself.
 */
int tty_unregister_driver(struct tty_driver *driver)
{
	int i;
	struct ktermios *tp;
	void *p;

	if (driver->refcount)
		return -EBUSY;

	unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
				driver->num);
	mutex_lock(&tty_mutex);
	list_del(&driver->tty_drivers);
	mutex_unlock(&tty_mutex);

	/*
	 * Free the termios and termios_locked structures because
	 * we don't want to get memory leaks when modular tty
	 * drivers are removed from the kernel.
	 */
	for (i = 0; i < driver->num; i++) {
		tp = driver->termios[i];
		if (tp) {
			driver->termios[i] = NULL;
			kfree(tp);
		}
		tp = driver->termios_locked[i];
		if (tp) {
			driver->termios_locked[i] = NULL;
			kfree(tp);
		}
		if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV))
			tty_unregister_device(driver, i);
	}
	p = driver->ttys;
	proc_tty_unregister_driver(driver);
	driver->ttys = NULL;
	driver->termios = driver->termios_locked = NULL;
	kfree(p);
	cdev_del(&driver->cdev);
	return 0;
}
EXPORT_SYMBOL(tty_unregister_driver);

dev_t tty_devnum(struct tty_struct *tty)
{
	return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
}
EXPORT_SYMBOL(tty_devnum);

void proc_clear_tty(struct task_struct *p)
{
	spin_lock_irq(&p->sighand->siglock);
	p->signal->tty = NULL;
	spin_unlock_irq(&p->sighand->siglock);
}
EXPORT_SYMBOL(proc_clear_tty);

/* Called under the sighand lock */

static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
{
	if (tty) {
		unsigned long flags;
		/* We should not have a session or pgrp to put here but.... */
		spin_lock_irqsave(&tty->ctrl_lock, flags);
		put_pid(tty->session);
		put_pid(tty->pgrp);
		tty->pgrp = get_pid(task_pgrp(tsk));
		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
		tty->session = get_pid(task_session(tsk));
	}
	put_pid(tsk->signal->tty_old_pgrp);
	tsk->signal->tty = tty;
	tsk->signal->tty_old_pgrp = NULL;
}

static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
{
	spin_lock_irq(&tsk->sighand->siglock);
	__proc_set_tty(tsk, tty);
	spin_unlock_irq(&tsk->sighand->siglock);
}

struct tty_struct *get_current_tty(void)
{
	struct tty_struct *tty;
	WARN_ON_ONCE(!mutex_is_locked(&tty_mutex));
	tty = current->signal->tty;
	/*
	 * session->tty can be changed/cleared from under us, make sure we
	 * issue the load. The obtained pointer, when not NULL, is valid as
	 * long as we hold tty_mutex.
	 */
	barrier();
	return tty;
}
EXPORT_SYMBOL_GPL(get_current_tty);

/*
 * Initialize the console device. This is called *early*, so
 * we can't necessarily depend on lots of kernel help here.
 * Just do some early initializations, and do the complex setup
 * later.
 */
void __init console_init(void)
{
	initcall_t *call;

	/* Setup the default TTY line discipline. */
	(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);

	/*
	 * set up the console device so that later boot sequences can
	 * inform about problems etc..
	 */
	call = __con_initcall_start;
	while (call < __con_initcall_end) {
		(*call)();
		call++;
	}
}

static int __init tty_class_init(void)
{
	tty_class = class_create(THIS_MODULE, "tty");
	if (IS_ERR(tty_class))
		return PTR_ERR(tty_class);
	return 0;
}

postcore_initcall(tty_class_init);

/* 3/2004 jmc: why do these devices exist? */

static struct cdev tty_cdev, console_cdev;
#ifdef CONFIG_UNIX98_PTYS
static struct cdev ptmx_cdev;
#endif
#ifdef CONFIG_VT
static struct cdev vc0_cdev;
#endif

/*
 * Ok, now we can initialize the rest of the tty devices and can count
 * on memory allocations, interrupts etc..
 */
static int __init tty_init(void)
{
	cdev_init(&tty_cdev, &tty_fops);
	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
		panic("Couldn't register /dev/tty driver\n");
	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), "tty");

	cdev_init(&console_cdev, &console_fops);
	if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0)
		panic("Couldn't register /dev/console driver\n");
	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 1), "console");

#ifdef CONFIG_UNIX98_PTYS
	cdev_init(&ptmx_cdev, &ptmx_fops);
	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
		panic("Couldn't register /dev/ptmx driver\n");
	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), "ptmx");
#endif

#ifdef CONFIG_VT
	cdev_init(&vc0_cdev, &console_fops);
	if (cdev_add(&vc0_cdev, MKDEV(TTY_MAJOR, 0), 1) ||
	    register_chrdev_region(MKDEV(TTY_MAJOR, 0), 1, "/dev/vc/0") < 0)
		panic("Couldn't register /dev/tty0 driver\n");
	device_create(tty_class, NULL, MKDEV(TTY_MAJOR, 0), "tty0");

	vty_init();
#endif
	return 0;
}
module_init(tty_init);