summaryrefslogtreecommitdiff
path: root/include/drm/drm_dp_helper.h
blob: b4f58914bf7d9374342c938ecada9ba52a7c82ae (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
/*
 * Copyright © 2008 Keith Packard
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#ifndef _DRM_DP_HELPER_H_
#define _DRM_DP_HELPER_H_

#include <linux/types.h>
#include <linux/i2c.h>
#include <linux/delay.h>

/*
 * Unless otherwise noted, all values are from the DP 1.1a spec.  Note that
 * DP and DPCD versions are independent.  Differences from 1.0 are not noted,
 * 1.0 devices basically don't exist in the wild.
 *
 * Abbreviations, in chronological order:
 *
 * eDP: Embedded DisplayPort version 1
 * DPI: DisplayPort Interoperability Guideline v1.1a
 * 1.2: DisplayPort 1.2
 *
 * 1.2 formally includes both eDP and DPI definitions.
 */

#define DP_AUX_I2C_WRITE		0x0
#define DP_AUX_I2C_READ			0x1
#define DP_AUX_I2C_STATUS		0x2
#define DP_AUX_I2C_MOT			0x4
#define DP_AUX_NATIVE_WRITE		0x8
#define DP_AUX_NATIVE_READ		0x9

#define DP_AUX_NATIVE_REPLY_ACK		(0x0 << 0)
#define DP_AUX_NATIVE_REPLY_NACK	(0x1 << 0)
#define DP_AUX_NATIVE_REPLY_DEFER	(0x2 << 0)
#define DP_AUX_NATIVE_REPLY_MASK	(0x3 << 0)

#define DP_AUX_I2C_REPLY_ACK		(0x0 << 2)
#define DP_AUX_I2C_REPLY_NACK		(0x1 << 2)
#define DP_AUX_I2C_REPLY_DEFER		(0x2 << 2)
#define DP_AUX_I2C_REPLY_MASK		(0x3 << 2)

/* AUX CH addresses */
/* DPCD */
#define DP_DPCD_REV                         0x000

#define DP_MAX_LINK_RATE                    0x001

#define DP_MAX_LANE_COUNT                   0x002
# define DP_MAX_LANE_COUNT_MASK		    0x1f
# define DP_TPS3_SUPPORTED		    (1 << 6) /* 1.2 */
# define DP_ENHANCED_FRAME_CAP		    (1 << 7)

#define DP_MAX_DOWNSPREAD                   0x003
# define DP_NO_AUX_HANDSHAKE_LINK_TRAINING  (1 << 6)

#define DP_NORP                             0x004

#define DP_DOWNSTREAMPORT_PRESENT           0x005
# define DP_DWN_STRM_PORT_PRESENT           (1 << 0)
# define DP_DWN_STRM_PORT_TYPE_MASK         0x06
# define DP_DWN_STRM_PORT_TYPE_DP           (0 << 1)
# define DP_DWN_STRM_PORT_TYPE_ANALOG       (1 << 1)
# define DP_DWN_STRM_PORT_TYPE_TMDS         (2 << 1)
# define DP_DWN_STRM_PORT_TYPE_OTHER        (3 << 1)
# define DP_FORMAT_CONVERSION               (1 << 3)
# define DP_DETAILED_CAP_INFO_AVAILABLE	    (1 << 4) /* DPI */

#define DP_MAIN_LINK_CHANNEL_CODING         0x006

#define DP_DOWN_STREAM_PORT_COUNT	    0x007
# define DP_PORT_COUNT_MASK		    0x0f
# define DP_MSA_TIMING_PAR_IGNORED	    (1 << 6) /* eDP */
# define DP_OUI_SUPPORT			    (1 << 7)

#define DP_I2C_SPEED_CAP		    0x00c    /* DPI */
# define DP_I2C_SPEED_1K		    0x01
# define DP_I2C_SPEED_5K		    0x02
# define DP_I2C_SPEED_10K		    0x04
# define DP_I2C_SPEED_100K		    0x08
# define DP_I2C_SPEED_400K		    0x10
# define DP_I2C_SPEED_1M		    0x20

#define DP_EDP_CONFIGURATION_CAP            0x00d   /* XXX 1.2? */
#define DP_TRAINING_AUX_RD_INTERVAL         0x00e   /* XXX 1.2? */

/* Multiple stream transport */
#define DP_MSTM_CAP			    0x021   /* 1.2 */
# define DP_MST_CAP			    (1 << 0)

#define DP_PSR_SUPPORT                      0x070   /* XXX 1.2? */
# define DP_PSR_IS_SUPPORTED                1
#define DP_PSR_CAPS                         0x071   /* XXX 1.2? */
# define DP_PSR_NO_TRAIN_ON_EXIT            1
# define DP_PSR_SETUP_TIME_330              (0 << 1)
# define DP_PSR_SETUP_TIME_275              (1 << 1)
# define DP_PSR_SETUP_TIME_220              (2 << 1)
# define DP_PSR_SETUP_TIME_165              (3 << 1)
# define DP_PSR_SETUP_TIME_110              (4 << 1)
# define DP_PSR_SETUP_TIME_55               (5 << 1)
# define DP_PSR_SETUP_TIME_0                (6 << 1)
# define DP_PSR_SETUP_TIME_MASK             (7 << 1)
# define DP_PSR_SETUP_TIME_SHIFT            1

/*
 * 0x80-0x8f describe downstream port capabilities, but there are two layouts
 * based on whether DP_DETAILED_CAP_INFO_AVAILABLE was set.  If it was not,
 * each port's descriptor is one byte wide.  If it was set, each port's is
 * four bytes wide, starting with the one byte from the base info.  As of
 * DP interop v1.1a only VGA defines additional detail.
 */

/* offset 0 */
#define DP_DOWNSTREAM_PORT_0		    0x80
# define DP_DS_PORT_TYPE_MASK		    (7 << 0)
# define DP_DS_PORT_TYPE_DP		    0
# define DP_DS_PORT_TYPE_VGA		    1
# define DP_DS_PORT_TYPE_DVI		    2
# define DP_DS_PORT_TYPE_HDMI		    3
# define DP_DS_PORT_TYPE_NON_EDID	    4
# define DP_DS_PORT_HPD			    (1 << 3)
/* offset 1 for VGA is maximum megapixels per second / 8 */
/* offset 2 */
# define DP_DS_VGA_MAX_BPC_MASK		    (3 << 0)
# define DP_DS_VGA_8BPC			    0
# define DP_DS_VGA_10BPC		    1
# define DP_DS_VGA_12BPC		    2
# define DP_DS_VGA_16BPC		    3

/* link configuration */
#define	DP_LINK_BW_SET		            0x100
# define DP_LINK_BW_1_62		    0x06
# define DP_LINK_BW_2_7			    0x0a
# define DP_LINK_BW_5_4			    0x14    /* 1.2 */

#define DP_LANE_COUNT_SET	            0x101
# define DP_LANE_COUNT_MASK		    0x0f
# define DP_LANE_COUNT_ENHANCED_FRAME_EN    (1 << 7)

#define DP_TRAINING_PATTERN_SET	            0x102
# define DP_TRAINING_PATTERN_DISABLE	    0
# define DP_TRAINING_PATTERN_1		    1
# define DP_TRAINING_PATTERN_2		    2
# define DP_TRAINING_PATTERN_3		    3	    /* 1.2 */
# define DP_TRAINING_PATTERN_MASK	    0x3

# define DP_LINK_QUAL_PATTERN_DISABLE	    (0 << 2)
# define DP_LINK_QUAL_PATTERN_D10_2	    (1 << 2)
# define DP_LINK_QUAL_PATTERN_ERROR_RATE    (2 << 2)
# define DP_LINK_QUAL_PATTERN_PRBS7	    (3 << 2)
# define DP_LINK_QUAL_PATTERN_MASK	    (3 << 2)

# define DP_RECOVERED_CLOCK_OUT_EN	    (1 << 4)
# define DP_LINK_SCRAMBLING_DISABLE	    (1 << 5)

# define DP_SYMBOL_ERROR_COUNT_BOTH	    (0 << 6)
# define DP_SYMBOL_ERROR_COUNT_DISPARITY    (1 << 6)
# define DP_SYMBOL_ERROR_COUNT_SYMBOL	    (2 << 6)
# define DP_SYMBOL_ERROR_COUNT_MASK	    (3 << 6)

#define DP_TRAINING_LANE0_SET		    0x103
#define DP_TRAINING_LANE1_SET		    0x104
#define DP_TRAINING_LANE2_SET		    0x105
#define DP_TRAINING_LANE3_SET		    0x106

# define DP_TRAIN_VOLTAGE_SWING_MASK	    0x3
# define DP_TRAIN_VOLTAGE_SWING_SHIFT	    0
# define DP_TRAIN_MAX_SWING_REACHED	    (1 << 2)
# define DP_TRAIN_VOLTAGE_SWING_400	    (0 << 0)
# define DP_TRAIN_VOLTAGE_SWING_600	    (1 << 0)
# define DP_TRAIN_VOLTAGE_SWING_800	    (2 << 0)
# define DP_TRAIN_VOLTAGE_SWING_1200	    (3 << 0)

# define DP_TRAIN_PRE_EMPHASIS_MASK	    (3 << 3)
# define DP_TRAIN_PRE_EMPHASIS_0	    (0 << 3)
# define DP_TRAIN_PRE_EMPHASIS_3_5	    (1 << 3)
# define DP_TRAIN_PRE_EMPHASIS_6	    (2 << 3)
# define DP_TRAIN_PRE_EMPHASIS_9_5	    (3 << 3)

# define DP_TRAIN_PRE_EMPHASIS_SHIFT	    3
# define DP_TRAIN_MAX_PRE_EMPHASIS_REACHED  (1 << 5)

#define DP_DOWNSPREAD_CTRL		    0x107
# define DP_SPREAD_AMP_0_5		    (1 << 4)
# define DP_MSA_TIMING_PAR_IGNORE_EN	    (1 << 7) /* eDP */

#define DP_MAIN_LINK_CHANNEL_CODING_SET	    0x108
# define DP_SET_ANSI_8B10B		    (1 << 0)

#define DP_I2C_SPEED_CONTROL_STATUS	    0x109   /* DPI */
/* bitmask as for DP_I2C_SPEED_CAP */

#define DP_EDP_CONFIGURATION_SET            0x10a   /* XXX 1.2? */

#define DP_MSTM_CTRL			    0x111   /* 1.2 */
# define DP_MST_EN			    (1 << 0)
# define DP_UP_REQ_EN			    (1 << 1)
# define DP_UPSTREAM_IS_SRC		    (1 << 2)

#define DP_PSR_EN_CFG			    0x170   /* XXX 1.2? */
# define DP_PSR_ENABLE			    (1 << 0)
# define DP_PSR_MAIN_LINK_ACTIVE	    (1 << 1)
# define DP_PSR_CRC_VERIFICATION	    (1 << 2)
# define DP_PSR_FRAME_CAPTURE		    (1 << 3)

#define DP_SINK_COUNT			    0x200
/* prior to 1.2 bit 7 was reserved mbz */
# define DP_GET_SINK_COUNT(x)		    ((((x) & 0x80) >> 1) | ((x) & 0x3f))
# define DP_SINK_CP_READY		    (1 << 6)

#define DP_DEVICE_SERVICE_IRQ_VECTOR	    0x201
# define DP_REMOTE_CONTROL_COMMAND_PENDING  (1 << 0)
# define DP_AUTOMATED_TEST_REQUEST	    (1 << 1)
# define DP_CP_IRQ			    (1 << 2)
# define DP_SINK_SPECIFIC_IRQ		    (1 << 6)

#define DP_LANE0_1_STATUS		    0x202
#define DP_LANE2_3_STATUS		    0x203
# define DP_LANE_CR_DONE		    (1 << 0)
# define DP_LANE_CHANNEL_EQ_DONE	    (1 << 1)
# define DP_LANE_SYMBOL_LOCKED		    (1 << 2)

#define DP_CHANNEL_EQ_BITS (DP_LANE_CR_DONE |		\
			    DP_LANE_CHANNEL_EQ_DONE |	\
			    DP_LANE_SYMBOL_LOCKED)

#define DP_LANE_ALIGN_STATUS_UPDATED	    0x204

#define DP_INTERLANE_ALIGN_DONE		    (1 << 0)
#define DP_DOWNSTREAM_PORT_STATUS_CHANGED   (1 << 6)
#define DP_LINK_STATUS_UPDATED		    (1 << 7)

#define DP_SINK_STATUS			    0x205

#define DP_RECEIVE_PORT_0_STATUS	    (1 << 0)
#define DP_RECEIVE_PORT_1_STATUS	    (1 << 1)

#define DP_ADJUST_REQUEST_LANE0_1	    0x206
#define DP_ADJUST_REQUEST_LANE2_3	    0x207
# define DP_ADJUST_VOLTAGE_SWING_LANE0_MASK  0x03
# define DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT 0
# define DP_ADJUST_PRE_EMPHASIS_LANE0_MASK   0x0c
# define DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT  2
# define DP_ADJUST_VOLTAGE_SWING_LANE1_MASK  0x30
# define DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT 4
# define DP_ADJUST_PRE_EMPHASIS_LANE1_MASK   0xc0
# define DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT  6

#define DP_TEST_REQUEST			    0x218
# define DP_TEST_LINK_TRAINING		    (1 << 0)
# define DP_TEST_LINK_VIDEO_PATTERN	    (1 << 1)
# define DP_TEST_LINK_EDID_READ		    (1 << 2)
# define DP_TEST_LINK_PHY_TEST_PATTERN	    (1 << 3) /* DPCD >= 1.1 */
# define DP_TEST_LINK_FAUX_PATTERN	    (1 << 4) /* DPCD >= 1.2 */

#define DP_TEST_LINK_RATE		    0x219
# define DP_LINK_RATE_162		    (0x6)
# define DP_LINK_RATE_27		    (0xa)

#define DP_TEST_LANE_COUNT		    0x220

#define DP_TEST_PATTERN			    0x221

#define DP_TEST_CRC_R_CR		    0x240
#define DP_TEST_CRC_G_Y			    0x242
#define DP_TEST_CRC_B_CB		    0x244

#define DP_TEST_SINK_MISC		    0x246
#define DP_TEST_CRC_SUPPORTED		    (1 << 5)

#define DP_TEST_RESPONSE		    0x260
# define DP_TEST_ACK			    (1 << 0)
# define DP_TEST_NAK			    (1 << 1)
# define DP_TEST_EDID_CHECKSUM_WRITE	    (1 << 2)

#define DP_TEST_SINK			    0x270
#define DP_TEST_SINK_START	    (1 << 0)

#define DP_SOURCE_OUI			    0x300
#define DP_SINK_OUI			    0x400
#define DP_BRANCH_OUI			    0x500

#define DP_SET_POWER                        0x600
# define DP_SET_POWER_D0                    0x1
# define DP_SET_POWER_D3                    0x2
# define DP_SET_POWER_MASK                  0x3

#define DP_PSR_ERROR_STATUS                 0x2006  /* XXX 1.2? */
# define DP_PSR_LINK_CRC_ERROR              (1 << 0)
# define DP_PSR_RFB_STORAGE_ERROR           (1 << 1)

#define DP_PSR_ESI                          0x2007  /* XXX 1.2? */
# define DP_PSR_CAPS_CHANGE                 (1 << 0)

#define DP_PSR_STATUS                       0x2008  /* XXX 1.2? */
# define DP_PSR_SINK_INACTIVE               0
# define DP_PSR_SINK_ACTIVE_SRC_SYNCED      1
# define DP_PSR_SINK_ACTIVE_RFB             2
# define DP_PSR_SINK_ACTIVE_SINK_SYNCED     3
# define DP_PSR_SINK_ACTIVE_RESYNC          4
# define DP_PSR_SINK_INTERNAL_ERROR         7
# define DP_PSR_SINK_STATE_MASK             0x07

#define MODE_I2C_START	1
#define MODE_I2C_WRITE	2
#define MODE_I2C_READ	4
#define MODE_I2C_STOP	8

/**
 * struct i2c_algo_dp_aux_data - driver interface structure for i2c over dp
 * 				 aux algorithm
 * @running: set by the algo indicating whether an i2c is ongoing or whether
 * 	     the i2c bus is quiescent
 * @address: i2c target address for the currently ongoing transfer
 * @aux_ch: driver callback to transfer a single byte of the i2c payload
 */
struct i2c_algo_dp_aux_data {
	bool running;
	u16 address;
	int (*aux_ch) (struct i2c_adapter *adapter,
		       int mode, uint8_t write_byte,
		       uint8_t *read_byte);
};

int
i2c_dp_aux_add_bus(struct i2c_adapter *adapter);


#define DP_LINK_STATUS_SIZE	   6
bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
			  int lane_count);
bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
			      int lane_count);
u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
				     int lane);
u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
					  int lane);

#define DP_RECEIVER_CAP_SIZE		0xf
#define EDP_PSR_RECEIVER_CAP_SIZE	2

void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]);
void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]);

u8 drm_dp_link_rate_to_bw_code(int link_rate);
int drm_dp_bw_code_to_link_rate(u8 link_bw);

struct edp_sdp_header {
	u8 HB0; /* Secondary Data Packet ID */
	u8 HB1; /* Secondary Data Packet Type */
	u8 HB2; /* 7:5 reserved, 4:0 revision number */
	u8 HB3; /* 7:5 reserved, 4:0 number of valid data bytes */
} __packed;

#define EDP_SDP_HEADER_REVISION_MASK		0x1F
#define EDP_SDP_HEADER_VALID_PAYLOAD_BYTES	0x1F

struct edp_vsc_psr {
	struct edp_sdp_header sdp_header;
	u8 DB0; /* Stereo Interface */
	u8 DB1; /* 0 - PSR State; 1 - Update RFB; 2 - CRC Valid */
	u8 DB2; /* CRC value bits 7:0 of the R or Cr component */
	u8 DB3; /* CRC value bits 15:8 of the R or Cr component */
	u8 DB4; /* CRC value bits 7:0 of the G or Y component */
	u8 DB5; /* CRC value bits 15:8 of the G or Y component */
	u8 DB6; /* CRC value bits 7:0 of the B or Cb component */
	u8 DB7; /* CRC value bits 15:8 of the B or Cb component */
	u8 DB8_31[24]; /* Reserved */
} __packed;

#define EDP_VSC_PSR_STATE_ACTIVE	(1<<0)
#define EDP_VSC_PSR_UPDATE_RFB		(1<<1)
#define EDP_VSC_PSR_CRC_VALUES_VALID	(1<<2)

static inline int
drm_dp_max_link_rate(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
	return drm_dp_bw_code_to_link_rate(dpcd[DP_MAX_LINK_RATE]);
}

static inline u8
drm_dp_max_lane_count(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
	return dpcd[DP_MAX_LANE_COUNT] & DP_MAX_LANE_COUNT_MASK;
}

static inline bool
drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
	return dpcd[DP_DPCD_REV] >= 0x11 &&
		(dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);
}

/*
 * DisplayPort AUX channel
 */

/**
 * struct drm_dp_aux_msg - DisplayPort AUX channel transaction
 * @address: address of the (first) register to access
 * @request: contains the type of transaction (see DP_AUX_* macros)
 * @reply: upon completion, contains the reply type of the transaction
 * @buffer: pointer to a transmission or reception buffer
 * @size: size of @buffer
 */
struct drm_dp_aux_msg {
	unsigned int address;
	u8 request;
	u8 reply;
	void *buffer;
	size_t size;
};

/**
 * struct drm_dp_aux - DisplayPort AUX channel
 * @ddc: I2C adapter that can be used for I2C-over-AUX communication
 * @dev: pointer to struct device that is the parent for this AUX channel
 * @transfer: transfers a message representing a single AUX transaction
 *
 * The .dev field should be set to a pointer to the device that implements
 * the AUX channel.
 *
 * The .name field may be used to specify the name of the I2C adapter. If set to
 * NULL, dev_name() of .dev will be used.
 *
 * Drivers provide a hardware-specific implementation of how transactions
 * are executed via the .transfer() function. A pointer to a drm_dp_aux_msg
 * structure describing the transaction is passed into this function. Upon
 * success, the implementation should return the number of payload bytes
 * that were transferred, or a negative error-code on failure. Helpers
 * propagate errors from the .transfer() function, with the exception of
 * the -EBUSY error, which causes a transaction to be retried. On a short,
 * helpers will return -EPROTO to make it simpler to check for failure.
 *
 * An AUX channel can also be used to transport I2C messages to a sink. A
 * typical application of that is to access an EDID that's present in the
 * sink device. The .transfer() function can also be used to execute such
 * transactions. The drm_dp_aux_register_i2c_bus() function registers an
 * I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers
 * should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.
 */
struct drm_dp_aux {
	const char *name;
	struct i2c_adapter ddc;
	struct device *dev;

	ssize_t (*transfer)(struct drm_dp_aux *aux,
			    struct drm_dp_aux_msg *msg);
};

ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
			 void *buffer, size_t size);
ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
			  void *buffer, size_t size);

/**
 * drm_dp_dpcd_readb() - read a single byte from the DPCD
 * @aux: DisplayPort AUX channel
 * @offset: address of the register to read
 * @valuep: location where the value of the register will be stored
 *
 * Returns the number of bytes transferred (1) on success, or a negative
 * error code on failure.
 */
static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,
					unsigned int offset, u8 *valuep)
{
	return drm_dp_dpcd_read(aux, offset, valuep, 1);
}

/**
 * drm_dp_dpcd_writeb() - write a single byte to the DPCD
 * @aux: DisplayPort AUX channel
 * @offset: address of the register to write
 * @value: value to write to the register
 *
 * Returns the number of bytes transferred (1) on success, or a negative
 * error code on failure.
 */
static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
					 unsigned int offset, u8 value)
{
	return drm_dp_dpcd_write(aux, offset, &value, 1);
}

int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
				 u8 status[DP_LINK_STATUS_SIZE]);

/*
 * DisplayPort link
 */
#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)

struct drm_dp_link {
	unsigned char revision;
	unsigned int rate;
	unsigned int num_lanes;
	unsigned long capabilities;
};

int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);

int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);
void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);

#endif /* _DRM_DP_HELPER_H_ */