GPS: GPS Char Driver for Texas Instrument's Connectivity Chip.

This enables the GPS driver for TI WL128x BT/FM/GPS combo devices.
It will provide a character device for the TI GPS host software to
access the GPS core on the WL128x.
Bug 933797

Change-Id: If0ea53a1b246a88fc895a95599d8bd38689b72fc
Signed-off-by: Satish Chandra <x0141690@ti.com>
Reviewed-on: http://git-master/r/90110
Reviewed-by: Automatic_Commit_Validation_User
Tested-by: Rakesh Goyal <rgoyal@nvidia.com>
Reviewed-by: Maria Bornski <mbornski@nvidia.com>
Reviewed-by: Sachin Nikam <snikam@nvidia.com>

3 files changed, 812 insertions, 0 deletions

diff --git a/drivers/misc/ti-st/Kconfig b/drivers/misc/ti-st/Kconfig
index abb5de1afce3..8f20ddaf0949 100644
--- a/drivers/misc/ti-st/Kconfig
+++ b/drivers/misc/ti-st/Kconfig
@@ -14,4 +14,11 @@ config TI_ST
 	  are returned to relevant protocol drivers based on their
 	  packet types.
 
+config ST_GPS
+	tristate "gps driver for ST"
+	select TI_ST
+	help
+	  This enables the GPS driver for TI WL128x BT/FM/GPS combo devices.
+	  It will provide a character device for the TI GPS host software to
+	  access the GPS core on the WL128x.
 endmenu
diff --git a/drivers/misc/ti-st/Makefile b/drivers/misc/ti-st/Makefile
index 78d7ebb14749..3f6d990912c2 100644
--- a/drivers/misc/ti-st/Makefile
+++ b/drivers/misc/ti-st/Makefile
@@ -4,3 +4,4 @@
 #
 obj-$(CONFIG_TI_ST) 		+= st_drv.o
 st_drv-objs			:= st_core.o st_kim.o st_ll.o
+obj-$(CONFIG_ST_GPS)            += gps_drv.o
diff --git a/drivers/misc/ti-st/gps_drv.c b/drivers/misc/ti-st/gps_drv.c
new file mode 100644
index 000000000000..17ca92dd177b
--- /dev/null
+++ b/drivers/misc/ti-st/gps_drv.c
@@ -0,0 +1,804 @@
+/*
+ *   GPS Char Driver for Texas Instrument's Connectivity Chip.
+ *   Copyright (C) 2009 Texas Instruments
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License version 2 as
+ *   published by the Free Software Foundation.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/cdev.h>
+#include <linux/fs.h>
+#include <linux/device.h>
+
+#include <linux/uaccess.h>
+#include <linux/tty.h>
+#include <linux/sched.h>
+
+#include <linux/delay.h>
+#include <linux/firmware.h>
+#include <linux/platform_device.h>
+#include <linux/poll.h>
+#include <linux/skbuff.h>
+#include <linux/interrupt.h>
+
+#include <linux/ti_wilink_st.h>
+
+#undef VERBOSE
+#undef DEBUG
+
+/* Debug macros*/
+#if defined(DEBUG)		/* limited debug messages */
+#define GPSDRV_DBG(fmt, arg...)  \
+	printk(KERN_INFO "[GPS] (gpsdrv):"fmt"\n" , ## arg)
+#define GPSDRV_VER(fmt, arg...)
+#elif defined(VERBOSE)		/* very verbose */
+#define GPSDRV_DBG(fmt, arg...)  \
+	printk(KERN_INFO "[GPS] (gpsdrv):"fmt"\n" , ## arg)
+#define GPSDRV_VER(fmt, arg...)  \
+	printk(KERN_INFO "[GPS] (gpsdrv):"fmt"\n" , ## arg)
+#define GPSDRV_ERR(fmt, arg...)  \
+	printk(KERN_ERR "[GPS] (gpsdrv):"fmt"\n" , ## arg)
+#else /* Error msgs only */
+#define GPSDRV_ERR(fmt, arg...)  \
+	printk(KERN_ERR "[GPS] (gpsdrv):"fmt"\n" , ## arg)
+#define GPSDRV_VER(fmt, arg...)
+#define GPSDRV_DBG(fmt, arg...)
+#endif
+
+static void gpsdrv_tsklet_write(unsigned long data);
+
+/* List of error codes returned by the gps driver*/
+enum {
+	GPS_ERR_FAILURE = -1,	/* check struct */
+	GPS_SUCCESS,
+	GPS_ERR_CLASS = -15,
+	GPS_ERR_CPY_TO_USR,
+	GPS_ERR_CPY_FRM_USR,
+	GPS_ERR_UNKNOWN,
+};
+
+/* Channel-9 details for GPS */
+#define GPS_CH9_PKT_HDR_SIZE		4
+#define GPS_CH9_PKT_NUMBER		0x9
+#define GPS_CH9_OP_WRITE		0x1
+#define GPS_CH9_OP_READ			0x2
+#define GPS_CH9_OP_COMPLETED_EVT	0x3
+
+/* Macros for Syncronising GPS registration and other R/W/ICTL operations */
+#define GPS_ST_REGISTERED	0
+#define GPS_ST_RUNNING		1
+
+/* Read time out defined to 10 seconds */
+#define GPSDRV_READ_TIMEOUT	10000
+/* Reg time out defined to 6 seconds */
+#define GPSDRV_REG_TIMEOUT	6000
+
+
+struct gpsdrv_event_hdr {
+	uint8_t opcode;
+	uint16_t plen;
+} __packed;
+
+/*
+ * struct gpsdrv_data - gps internal driver data
+ * @gpsdrv_reg_completed - completion to wait for registration
+ * @streg_cbdata - registration feedback
+ * @state - driver state
+ * @tx_count - TX throttling/unthrottling
+ * @st_write - write ptr from ST
+ * @rx_list - Rx data SKB queue
+ * @tx_list - Tx data SKB queue
+ * @gpsdrv_data_q - dataq checked up on poll/receive
+ * @lock - spin lock
+ * @gpsdrv_tx_tsklet - gps write task
+ */
+
+struct gpsdrv_data {
+	struct completion gpsdrv_reg_completed;
+	char streg_cbdata;
+	unsigned long state;
+	unsigned char tx_count;
+	long (*st_write) (struct sk_buff *skb);
+	struct sk_buff_head rx_list;
+	struct sk_buff_head tx_list;
+	wait_queue_head_t gpsdrv_data_q;
+	spinlock_t lock;
+	struct tasklet_struct gpsdrv_tx_tsklet;
+};
+
+#define DEVICE_NAME     "tigps"
+
+/***********Functions called from ST driver**********************************/
+
+/*  gpsdrv_st_recv Function
+ *  This is Called in from -- ST Core when a data is received
+ *  This is a registered callback with ST core when the gps driver registers
+ *  with ST.
+ *
+ *  Parameters:
+ *  @skb    : SKB buffer pointer which contains the incoming Ch-9 GPS data.
+ *  Returns:
+ *          GPS_SUCCESS - On Success
+ *          else suitable error code
+ */
+long gpsdrv_st_recv(void *arg, struct sk_buff *skb)
+{
+	struct gpsdrv_event_hdr gpsdrv_hdr = { 0x00, 0x0000 };
+	struct gpsdrv_data *hgps = (struct gpsdrv_data *)arg;
+
+	/* SKB is NULL */
+	if (NULL == skb) {
+		GPSDRV_ERR("Input SKB is NULL");
+		return GPS_ERR_FAILURE;
+	}
+
+	/* Sanity Check - To Check if the Rx Pkt is Channel -9 or not */
+	if (0x09 != skb->cb[0]) {
+		GPSDRV_ERR("Input SKB is not a Channel-9 packet");
+		return GPS_ERR_FAILURE;
+	}
+	/* Copy Ch-9 info to local structure */
+	memcpy(&gpsdrv_hdr, skb->data, GPS_CH9_PKT_HDR_SIZE - 1);
+	skb_pull(skb, GPS_CH9_PKT_HDR_SIZE - 1);
+
+	/* check if skb->len and gpsdrv_hdr.plen are equal */
+	if (skb->len != gpsdrv_hdr.plen) {
+		GPSDRV_ERR("Received corrupted packet - Length Mismatch");
+		return -EINVAL;
+	}
+#ifdef VERBOSE
+	printk(KERN_INFO"data start >>\n");
+	print_hex_dump(KERN_INFO, ">in>", DUMP_PREFIX_NONE,
+			16, 1, skb->data, skb->len, 0);
+	printk(KERN_INFO"\n<< end\n");
+#endif
+	/* Check the Opcode */
+	if ((gpsdrv_hdr.opcode != GPS_CH9_OP_READ) && (gpsdrv_hdr.opcode != \
+				GPS_CH9_OP_COMPLETED_EVT)) {
+		GPSDRV_ERR("Rec corrupt pkt opcode %x", gpsdrv_hdr.opcode);
+		return -EINVAL;
+	}
+
+	/* Strip Channel 9 packet information from SKB only
+	 * if the opcode is GPS_CH9_OP_READ and get AI2 packet
+	 */
+	if (GPS_CH9_OP_READ == gpsdrv_hdr.opcode) {
+		skb_queue_tail(&hgps->rx_list, skb);
+		wake_up_interruptible(&hgps->gpsdrv_data_q);
+	} else {
+		spin_lock(&hgps->lock);
+		/* The no. of Completed Packets is always 1
+		 * in case of Channel 9 as per spec.
+		 * Forcing it to 1 for precaution.
+		 */
+		hgps->tx_count = 1;
+		/* Check if Tx queue and Tx count not empty */
+		if (!skb_queue_empty(&hgps->tx_list)) {
+			/* Schedule the Tx-task let */
+			spin_unlock(&hgps->lock);
+			GPSDRV_VER(" Scheduling tasklet to write");
+			tasklet_schedule(&hgps->gpsdrv_tx_tsklet);
+		} else {
+			spin_unlock(&hgps->lock);
+		}
+
+		GPSDRV_VER(" Tx count = %x", hgps->tx_count);
+		/* Free the received command complete SKB */
+		kfree_skb(skb);
+	}
+
+	return GPS_SUCCESS;
+
+}
+
+/*  gpsdrv_st_cb Function
+ *  This is Called in from -- ST Core when the state is pending during
+ *  st_register. This is a registered callback with ST core when the gps
+ *  driver registers with ST.
+ *
+ *  Parameters:
+ *  @data   Status update of GPS registration
+ *  Returns: NULL
+ */
+void gpsdrv_st_cb(void *arg, char data)
+{
+	struct gpsdrv_data *hgps = (struct gpsdrv_data *)arg;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+	hgps->streg_cbdata = data;	/* ST registration callback  status */
+	complete_all(&hgps->gpsdrv_reg_completed);
+	return;
+}
+
+static struct st_proto_s gpsdrv_proto = {
+	.chnl_id = 0x09,
+	.max_frame_size = 1024,
+	.hdr_len = 3,
+	.offset_len_in_hdr = 1,
+	.len_size = 2,
+	.reserve = 1,
+	.recv = gpsdrv_st_recv,
+	.reg_complete_cb = gpsdrv_st_cb,
+};
+
+/** gpsdrv_tsklet_write Function
+ *  This tasklet function will be scheduled when there is a data in Tx queue
+ *  and GPS chip sent an command completion packet with non zero value.
+ *
+ *  Parameters :
+ *  @data  : data passed to tasklet function
+ *  Returns : NULL
+ */
+void gpsdrv_tsklet_write(unsigned long data)
+{
+	struct sk_buff *skb = NULL;
+	struct gpsdrv_data *hgps = (struct gpsdrv_data *)data;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+
+	spin_lock(&hgps->lock);
+
+	/* Perform sanity check of verifying the status
+	   to perform an st_write */
+	if (((!hgps->st_write) || (0 == hgps->tx_count))
+			|| ((skb_queue_empty(&hgps->tx_list)))) {
+		spin_unlock(&hgps->lock);
+		GPSDRV_ERR("Sanity check Failed exiting %s", __func__);
+		return;
+	}
+	/* hgps->tx_list not empty skb already present
+	 * dequeue the tx-data and perform a st_write
+	 */
+	hgps->tx_count--;
+	spin_unlock(&hgps->lock);
+	GPSDRV_VER(" Tx count in gpsdrv_tsklet_write = %x", hgps->tx_count);
+	skb = skb_dequeue(&hgps->tx_list);
+	hgps->st_write(skb);
+
+	return;
+}
+
+/*********Functions Called from GPS host***************************************/
+
+/** gpsdrv_open Function
+ *  This function will perform an register on ST driver.
+ *
+ *  Parameters :
+ *  @file  : File pointer for GPS char driver
+ *  @inod  :
+ *  Returns  GPS_SUCCESS -  on success
+ *           else suitable error code
+ */
+int gpsdrv_open(struct inode *inod, struct file *file)
+{
+	int ret = 0;
+	unsigned long timeout = GPSDRV_REG_TIMEOUT;
+	struct gpsdrv_data *hgps;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+
+	/* Allocate local resource memory */
+	hgps = kzalloc(sizeof(struct gpsdrv_data), GFP_KERNEL);
+	if (!(hgps)) {
+		GPSDRV_ERR("Can't allocate GPS data structure");
+		return -ENOMEM;
+	}
+
+	/* Initialize wait queue, skb queue head and
+	 * registration complete strucuture
+	 */
+	skb_queue_head_init(&hgps->rx_list);
+	skb_queue_head_init(&hgps->tx_list);
+	init_completion(&hgps->gpsdrv_reg_completed);
+	init_waitqueue_head(&hgps->gpsdrv_data_q);
+	spin_lock_init(&hgps->lock);
+
+	/* Check if GPS is already registered with ST */
+	if (test_and_set_bit(GPS_ST_REGISTERED, &hgps->state)) {
+		GPSDRV_ERR("GPS Registered/Registration in progress with ST"
+				" ,open called again?");
+		kfree(hgps);
+		return -EAGAIN;
+	}
+
+	/* Initialize  gpsdrv_reg_completed so as to wait for completion
+	 * on the same
+	 * if st_register returns with a PENDING status
+	 */
+	INIT_COMPLETION(hgps->gpsdrv_reg_completed);
+
+	gpsdrv_proto.priv_data = hgps;
+	/* Resgister GPS with ST */
+	ret = st_register(&gpsdrv_proto);
+	GPSDRV_VER(" st_register returned %d", ret);
+
+	/* If GPS Registration returned with error, then clear GPS_ST_REGISTERED
+	 * for future open calls and return the appropriate error code
+	 */
+	if (ret < 0 && ret != -EINPROGRESS) {
+		GPSDRV_ERR(" st_register failed");
+		clear_bit(GPS_ST_REGISTERED, &hgps->state);
+		if (ret == -EINPROGRESS)
+			return -EAGAIN;
+		return GPS_ERR_FAILURE;
+	}
+
+	/* if returned status is pending, wait for the completion */
+	if (ret == -EINPROGRESS) {
+		GPSDRV_VER(" GPS Register waiting for completion ");
+		timeout = wait_for_completion_timeout \
+		(&hgps->gpsdrv_reg_completed, msecs_to_jiffies(timeout));
+		/* Check for timed out condition */
+		if (0 == timeout) {
+			GPSDRV_ERR("GPS Device registration timed out");
+			clear_bit(GPS_ST_REGISTERED, &hgps->state);
+			return -ETIMEDOUT;
+		} else if (0 > hgps->streg_cbdata) {
+			GPSDRV_ERR("GPS Device Registration Failed-ST\n");
+			GPSDRV_ERR("RegCB called with ");
+			GPSDRV_ERR("Invalid value %d\n", hgps->streg_cbdata);
+			clear_bit(GPS_ST_REGISTERED, &hgps->state);
+			return -EAGAIN;
+		}
+	}
+	GPSDRV_DBG(" gps registration complete ");
+
+	/* Assign the write callback pointer */
+	hgps->st_write = gpsdrv_proto.write;
+	hgps->tx_count = 1;
+	file->private_data = hgps;	/* set drv data */
+	tasklet_init(&hgps->gpsdrv_tx_tsklet, (void *)gpsdrv_tsklet_write,
+			(unsigned long)hgps);
+	set_bit(GPS_ST_RUNNING, &hgps->state);
+
+	return GPS_SUCCESS;
+}
+
+/** gpsdrv_release Function
+ *  This function will un-registers from the ST driver.
+ *
+ *  Parameters :
+ *  @file  : File pointer for GPS char driver
+ *  @inod  :
+ *  Returns  GPS_SUCCESS -  on success
+ *           else suitable error code
+ */
+int gpsdrv_release(struct inode *inod, struct file *file)
+{
+	struct gpsdrv_data *hgps = file->private_data;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+
+	/* Disabling task-let 1st & then un-reg to avoid
+	 * tasklet getting scheduled
+	 */
+	tasklet_disable(&hgps->gpsdrv_tx_tsklet);
+	tasklet_kill(&hgps->gpsdrv_tx_tsklet);
+	/* Cleat registered bit if already registered */
+	if (test_and_clear_bit(GPS_ST_REGISTERED, &hgps->state)) {
+		if (st_unregister(&gpsdrv_proto) < 0) {
+			GPSDRV_ERR(" st_unregister failed");
+			/* Re-Enable the task-let if un-register fails */
+			tasklet_enable(&hgps->gpsdrv_tx_tsklet);
+			return GPS_ERR_FAILURE;
+		}
+	}
+
+	/* Reset Tx count value and st_write function pointer */
+	hgps->tx_count = 0;
+	hgps->st_write = NULL;
+	clear_bit(GPS_ST_RUNNING, &hgps->state);
+	GPSDRV_VER(" st_unregister success");
+
+	skb_queue_purge(&hgps->rx_list);
+	skb_queue_purge(&hgps->tx_list);
+	kfree(hgps);
+	file->private_data = NULL;
+
+	return GPS_SUCCESS;
+}
+
+/** gpsdrv_read Function
+ *  This function will wait till the data received from the ST driver
+ *  and then strips the GPS-Channel-9 header from the
+ *  incoming AI2 packet and then send it to GPS host application.
+ *
+ *  Parameters :
+ *  @file  : File pointer for GPS char driver
+ *  @data  : Data which needs to be passed to APP
+ *  @size  : Length of the data passesd
+ *  offset :
+ *  Returns  Size of AI2 packet received -  on success
+ *           else suitable error code
+ */
+ssize_t gpsdrv_read(struct file *file, char __user *data, size_t size,
+		loff_t *offset)
+{
+	int len = 0, error = 0;
+	struct sk_buff *skb = NULL;
+	unsigned long timeout = GPSDRV_READ_TIMEOUT;
+	struct gpsdrv_data *hgps;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+
+	/* Validate input parameters */
+	if ((NULL == file) || (((NULL == data) || (0 == size)))) {
+		GPSDRV_ERR("Invalid input params passed to %s", __func__);
+		return -EINVAL;
+	}
+
+	hgps = file->private_data;
+	/* Check if GPS is registered to perform read operation */
+	if (!test_bit(GPS_ST_RUNNING, &hgps->state)) {
+		GPSDRV_ERR("GPS Device is not running");
+		return -EINVAL;
+	}
+
+	/* cannot come here if poll-ed before reading
+	 * if not poll-ed wait on the same wait_q
+	 */
+	timeout = wait_event_interruptible_timeout(hgps->gpsdrv_data_q,
+		!skb_queue_empty(&hgps->rx_list), msecs_to_jiffies(timeout));
+	/* Check for timed out condition */
+	if (0 == timeout) {
+		GPSDRV_ERR("GPS Device Read timed out");
+		return -ETIMEDOUT;
+	}
+
+
+	/* hgps->rx_list not empty skb already present */
+	skb = skb_dequeue(&hgps->rx_list);
+
+	if (!skb) {
+		GPSDRV_ERR("Dequed SKB is NULL?");
+		return GPS_ERR_UNKNOWN;
+	} else if (skb->len > size) {
+		GPSDRV_DBG("SKB length is Greater than requested size ");
+		GPSDRV_DBG("Returning the available length of SKB\n");
+
+		error = copy_to_user(data, skb->data, size);
+		skb_pull(skb, size);
+
+		if (skb->len != 0)
+			skb_queue_head(&hgps->rx_list, skb);
+
+		/* printk(KERN_DEBUG  "gpsdrv: total size read= %d", size);*/
+		return size;
+	}
+
+#ifdef VERBOSE
+	print_hex_dump(KERN_INFO, ">in>", DUMP_PREFIX_NONE,
+			16, 1, skb->data, skb->len, 0);
+#endif
+
+	/* Forward the data to the user */
+	if (skb->len <= size) {
+		if (copy_to_user(data, skb->data, skb->len)) {
+			GPSDRV_ERR(" Unable to copy to user space");
+			/* Queue the skb back to head */
+			skb_queue_head(&hgps->rx_list, skb);
+			return GPS_ERR_CPY_TO_USR;
+		}
+	}
+
+	len = skb->len;
+	kfree_skb(skb);
+	/* printk(KERN_DEBUG  "gpsdrv: total size read= %d", len); */
+	return len;
+}
+/* gpsdrv_write Function
+ *  This function will pre-pend the GPS-Channel-9 header to the
+ *  incoming AI2 packet sent from the GPS host application.
+ *
+ *  Parameters :
+ *  @file   : File pointer for GPS char driver
+ *  @data   : AI2 packet data from GPS application
+ *  @size   : Size of the AI2 packet data
+ *  @offset :
+ *  Returns  Size of AI2 packet on success
+ *           else suitable error code
+ */
+ssize_t gpsdrv_write(struct file *file, const char __user *data,
+		size_t size, loff_t *offset)
+{
+	unsigned char channel = GPS_CH9_PKT_NUMBER; /* GPS Channel number */
+	/* Initialize gpsdrv_event_hdr with write opcode */
+	struct gpsdrv_event_hdr gpsdrv_hdr = { GPS_CH9_OP_WRITE, 0x0000 };
+	struct sk_buff *skb = NULL;
+	struct gpsdrv_data *hgps;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+	/* Validate input parameters */
+	if ((NULL == file) || (((NULL == data) || (0 == size)))) {
+		GPSDRV_ERR("Invalid input params passed to %s", __func__);
+		return -EINVAL;
+	}
+
+	hgps = file->private_data;
+
+	/* Check if GPS is registered to perform write operation */
+	if (!test_bit(GPS_ST_RUNNING, &hgps->state)) {
+		GPSDRV_ERR("GPS Device is not running");
+		return -EINVAL;
+	}
+
+	if (!hgps->st_write) {
+		GPSDRV_ERR(" Can't write to ST, hgps->st_write null ?");
+		return -EINVAL;
+	}
+
+
+	skb = alloc_skb(size + GPS_CH9_PKT_HDR_SIZE, GFP_ATOMIC);
+	/* Validate Created SKB */
+	if (NULL == skb) {
+		GPSDRV_ERR("Error aaloacting SKB");
+		return -ENOMEM;
+	}
+
+	/* Update chnl-9 information with plen=AI2 pckt size which is "size"*/
+	gpsdrv_hdr.plen = size;
+
+	/* PrePend Channel-9 header to AI2 packet and write to SKB */
+	memcpy(skb_put(skb, 1), &channel, 1);
+	memcpy(skb_put(skb, GPS_CH9_PKT_HDR_SIZE - 1), &gpsdrv_hdr,
+			GPS_CH9_PKT_HDR_SIZE - 1);
+
+	/* Forward the data from the user space to ST core */
+	if (copy_from_user(skb_put(skb, size), data, size)) {
+		GPSDRV_ERR(" Unable to copy from user space");
+		kfree_skb(skb);
+		return GPS_ERR_CPY_FRM_USR;
+	}
+
+#ifdef VERBOSE
+	GPSDRV_VER("start data..");
+	print_hex_dump(KERN_INFO, "<out<", DUMP_PREFIX_NONE,
+			16, 1, skb->data, size, 0);
+	GPSDRV_VER("\n..end data");
+#endif
+
+	/* Check if data can be sent to GPS chip
+	 * If not, add it to queue and that can be sent later
+	 */
+	spin_lock(&hgps->lock);
+	if (0 != hgps->tx_count) {
+		/* If TX Q is empty send current SKB;
+		 *  else, queue current SKB at end of tx_list queue and
+		 *  send first SKB in tx_list queue.
+		 */
+		hgps->tx_count--;
+		spin_unlock(&hgps->lock);
+
+		GPSDRV_VER(" Tx count in gpsdrv_write = %x", hgps->tx_count);
+
+		if (skb_queue_empty(&hgps->tx_list)) {
+			hgps->st_write(skb);
+		} else {
+			skb_queue_tail(&hgps->tx_list, skb);
+			hgps->st_write(skb_dequeue(&hgps->tx_list));
+		}
+	} else {
+		/* Add it to TX queue */
+		spin_unlock(&hgps->lock);
+		GPSDRV_VER(" SKB added to Tx queue ");
+		GPSDRV_VER("Tx count = %x ", hgps->tx_count);
+		skb_queue_tail(&hgps->tx_list, skb);
+		/* This is added for precaution in the case that there is a
+		 * context switch during the execution of the above lines.
+		 * Redundant otherwise.
+		 */
+		if ((0 != hgps->tx_count) && \
+				(!skb_queue_empty(&hgps->tx_list))) {
+			/* Schedule the Tx-task let */
+			GPSDRV_VER("Scheduling tasklet to write\n");
+			tasklet_schedule(&hgps->gpsdrv_tx_tsklet);
+		}
+	}
+
+	return size;
+}
+
+/** gpsdrv_ioctl Function
+ *  This will peform the functions as directed by the command and command
+ *  argument.
+ *
+ *  Parameters :
+ *  @file  : File pointer for GPS char driver
+ *  @cmd   : IOCTL Command
+ *  @arg   : Command argument for IOCTL command
+ *  Returns  GPS_SUCCESS on success
+ *           else suitable error code
+ */
+static long gpsdrv_ioctl(struct file *file,
+		unsigned int cmd, unsigned long arg)
+{
+	struct sk_buff *skb = NULL;
+	int		retCode = GPS_SUCCESS;
+	struct gpsdrv_data *hgps;
+
+	GPSDRV_DBG(" Inside %s", __func__);
+
+	/* Validate input parameters */
+	if ((NULL == file) || (0 == cmd)) {
+		GPSDRV_ERR("Invalid input parameters passed to %s", __func__);
+		return -EINVAL;
+	}
+
+	hgps = file->private_data;
+
+	/* Check if GPS is registered to perform IOCTL operation */
+	if (!test_bit(GPS_ST_RUNNING, &hgps->state)) {
+		GPSDRV_ERR("GPS Device is not running");
+		return -EINVAL;
+	}
+
+	switch (cmd) {
+	case TCFLSH:
+		GPSDRV_VER(" IOCTL TCFLSH invoked with %ld argument", arg);
+		switch (arg) {
+			/* purge Rx/Tx SKB list queues depending on arg value */
+		case TCIFLUSH:
+			skb_queue_purge(&hgps->rx_list);
+			break;
+		case TCOFLUSH:
+			skb_queue_purge(&hgps->tx_list);
+			break;
+		case TCIOFLUSH:
+			skb_queue_purge(&hgps->rx_list);
+			skb_queue_purge(&hgps->tx_list);
+			break;
+		default:
+			GPSDRV_ERR("Invalid Command passed for tcflush");
+			retCode = 0;
+			break;
+		}
+		break;
+	case FIONREAD:
+		/* Deque the SKB from the head if rx_list is not empty
+		 * And update the argument with skb->len to provide
+		 * the amount of data available in the available SKB
+		 */
+		skb = skb_dequeue(&hgps->rx_list);
+		if (skb != NULL) {
+			*(unsigned int *)arg = skb->len;
+			/* Re-Store the SKB for furtur Read operations */
+			skb_queue_head(&hgps->rx_list, skb);
+		} else {
+			*(unsigned int *)arg = 0;
+		}
+		GPSDRV_DBG("returning %d\n", *(unsigned int *)arg);
+
+		break;
+	default:
+		GPSDRV_DBG("Un-Identified IOCTL %d", cmd);
+		retCode = 0;
+		break;
+	}
+
+	return retCode;
+}
+
+/** gpsdrv_poll Function
+ *  This function will wait till some data is received to the gps driver from ST
+ *
+ *  Parameters :
+ *  @file  : File pointer for GPS char driver
+ *  @wait  : POLL wait information
+ *  Returns  status of POLL on success
+ *           else suitable error code
+ */
+static unsigned int gpsdrv_poll(struct file *file, poll_table *wait)
+{
+	unsigned long mask = 0;
+	struct gpsdrv_data *hgps = file->private_data;
+
+	/* Check if GPS is registered to perform read operation */
+	if (!test_bit(GPS_ST_RUNNING, &hgps->state)) {
+		GPSDRV_ERR("GPS Device is not running");
+		return -EINVAL;
+	}
+
+	/* Wait till data is signalled from gpsdrv_st_recv function
+	 *  with AI2 packet
+	 */
+	poll_wait(file, &hgps->gpsdrv_data_q, wait);
+
+	if (!skb_queue_empty(&hgps->rx_list))
+		mask |= POLLIN;	/* TODO: check app for mask */
+
+	return mask;
+}
+
+/* GPS Char driver function pointers
+ * These functions are called from USER space by pefroming File Operations
+ * on /dev/gps node exposed by this driver during init
+ */
+const struct file_operations gpsdrv_chrdev_ops = {
+	.owner = THIS_MODULE,
+	.open = gpsdrv_open,
+	.read = gpsdrv_read,
+	.write = gpsdrv_write,
+	.unlocked_ioctl = gpsdrv_ioctl,
+	.poll = gpsdrv_poll,
+	.release = gpsdrv_release,
+};
+
+/*********Functions called during insmod and delmod****************************/
+
+static int gpsdrv_major;		/* GPS major number */
+static struct class *gpsdrv_class;	/* GPS class during class_create */
+static struct device *gpsdrv_dev;	/* GPS dev during device_create */
+/** gpsdrv_init Function
+ *  This function Initializes the gps driver parametes and exposes
+ *  /dev/gps node to user space
+ *
+ *  Parameters : NULL
+ *  Returns  GPS_SUCCESS on success
+ *           else suitable error code
+ */
+static int __init gpsdrv_init(void)
+{
+
+	GPSDRV_DBG(" Inside %s", __func__);
+
+	/* Expose the device DEVICE_NAME to user space
+	 * And obtain the major number for the device
+	 */
+	gpsdrv_major = register_chrdev(0, DEVICE_NAME, \
+			&gpsdrv_chrdev_ops);
+	if (0 > gpsdrv_major) {
+		GPSDRV_ERR("Error when registering to char dev");
+		return GPS_ERR_FAILURE;
+	}
+	GPSDRV_VER("allocated %d, %d", gpsdrv_major, 0);
+
+	/*  udev */
+	gpsdrv_class = class_create(THIS_MODULE, DEVICE_NAME);
+	if (IS_ERR(gpsdrv_class)) {
+		GPSDRV_ERR(" Something went wrong in class_create");
+		unregister_chrdev(gpsdrv_major, DEVICE_NAME);
+		return GPS_ERR_CLASS;
+	}
+
+	gpsdrv_dev =
+		device_create(gpsdrv_class, NULL, MKDEV(gpsdrv_major, 0),
+				NULL, DEVICE_NAME);
+	if (IS_ERR(gpsdrv_dev)) {
+		GPSDRV_ERR(" Error in class_create");
+		unregister_chrdev(gpsdrv_major, DEVICE_NAME);
+		class_destroy(gpsdrv_class);
+		return GPS_ERR_CLASS;
+	}
+
+	return GPS_SUCCESS;
+}
+
+/** gpsdrv_exit Function
+ *  This function Destroys the gps driver parametes and /dev/gps node
+ *
+ *  Parameters : NULL
+ *  Returns   NULL
+ */
+static void __exit gpsdrv_exit(void)
+{
+	GPSDRV_DBG(" Inside %s", __func__);
+	GPSDRV_VER(" Bye.. freeing up %d", gpsdrv_major);
+
+	device_destroy(gpsdrv_class, MKDEV(gpsdrv_major, 0));
+	class_destroy(gpsdrv_class);
+	unregister_chrdev(gpsdrv_major, DEVICE_NAME);
+}
+
+module_init(gpsdrv_init);
+module_exit(gpsdrv_exit);
+MODULE_LICENSE("GPL");