drivers/media/video/gspca/sq905.c - kernel/msm - Gitiles

 /*
  * SQ905 subdriver
  *
  * Copyright (C) 2008, 2009 Adam Baker and Theodore Kilgore
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * any later version.
  *
  * 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
  */

 /*
  * History and Acknowledgments
  *
  * The original Linux driver for SQ905 based cameras was written by
  * Marcell Lengyel and furter developed by many other contributors
  * and is available from http://sourceforge.net/projects/sqcam/
  *
  * This driver takes advantage of the reverse engineering work done for
  * that driver and for libgphoto2 but shares no code with them.
  *
  * This driver has used as a base the finepix driver and other gspca
  * based drivers and may still contain code fragments taken from those
  * drivers.
  */

 #define MODULE_NAME "sq905"

 #include <linux/workqueue.h>
 #include <linux/slab.h>
 #include "gspca.h"

 MODULE_AUTHOR("Adam Baker <linux@baker-net.org.uk>, "
 		"Theodore Kilgore <kilgota@auburn.edu>");
 MODULE_DESCRIPTION("GSPCA/SQ905 USB Camera Driver");
 MODULE_LICENSE("GPL");

 /* Default timeouts, in ms */
 #define SQ905_CMD_TIMEOUT 500
 #define SQ905_DATA_TIMEOUT 1000

 /* Maximum transfer size to use. */
 #define SQ905_MAX_TRANSFER 0x8000
 #define FRAME_HEADER_LEN 64

 /* The known modes, or registers. These go in the "value" slot. */

 /* 00 is "none" obviously */

 #define SQ905_BULK_READ	0x03	/* precedes any bulk read */
 #define SQ905_COMMAND	0x06	/* precedes the command codes below */
 #define SQ905_PING	0x07	/* when reading an "idling" command */
 #define SQ905_READ_DONE 0xc0    /* ack bulk read completed */

 /* Any non-zero value in the bottom 2 bits of the 2nd byte of
  * the ID appears to indicate the camera can do 640*480. If the
  * LSB of that byte is set the image is just upside down, otherwise
  * it is rotated 180 degrees. */
 #define SQ905_HIRES_MASK	0x00000300
 #define SQ905_ORIENTATION_MASK	0x00000100

 /* Some command codes. These go in the "index" slot. */

 #define SQ905_ID      0xf0	/* asks for model string */
 #define SQ905_CONFIG  0x20	/* gets photo alloc. table, not used here */
 #define SQ905_DATA    0x30	/* accesses photo data, not used here */
 #define SQ905_CLEAR   0xa0	/* clear everything */
 #define SQ905_CAPTURE_LOW  0x60	/* Starts capture at 160x120 */
 #define SQ905_CAPTURE_MED  0x61	/* Starts capture at 320x240 */
 #define SQ905_CAPTURE_HIGH 0x62	/* Starts capture at 640x480 (some cams only) */
 /* note that the capture command also controls the output dimensions */

 /* Structure to hold all of our device specific stuff */
 struct sd {
 	struct gspca_dev gspca_dev;	/* !! must be the first item */

 	/*
 	 * Driver stuff
 	 */
 	struct work_struct work_struct;
 	struct workqueue_struct *work_thread;
 };

 static struct v4l2_pix_format sq905_mode[] = {
 	{ 160, 120, V4L2_PIX_FMT_SBGGR8, V4L2_FIELD_NONE,
 		.bytesperline = 160,
 		.sizeimage = 160 * 120,
 		.colorspace = V4L2_COLORSPACE_SRGB,
 		.priv = 0},
 	{ 320, 240, V4L2_PIX_FMT_SBGGR8, V4L2_FIELD_NONE,
 		.bytesperline = 320,
 		.sizeimage = 320 * 240,
 		.colorspace = V4L2_COLORSPACE_SRGB,
 		.priv = 0},
 	{ 640, 480, V4L2_PIX_FMT_SBGGR8, V4L2_FIELD_NONE,
 		.bytesperline = 640,
 		.sizeimage = 640 * 480,
 		.colorspace = V4L2_COLORSPACE_SRGB,
 		.priv = 0}
 };

 /*
  * Send a command to the camera.
  */
 static int sq905_command(struct gspca_dev *gspca_dev, u16 index)
 {
 	int ret;

 	gspca_dev->usb_buf[0] = '\0';
 	ret = usb_control_msg(gspca_dev->dev,
 			      usb_sndctrlpipe(gspca_dev->dev, 0),
 			      USB_REQ_SYNCH_FRAME,                /* request */
 			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			      SQ905_COMMAND, index, gspca_dev->usb_buf, 1,
 			      SQ905_CMD_TIMEOUT);
 	if (ret < 0) {
 		err("%s: usb_control_msg failed (%d)",
 			__func__, ret);
 		return ret;
 	}

 	ret = usb_control_msg(gspca_dev->dev,
 			      usb_sndctrlpipe(gspca_dev->dev, 0),
 			      USB_REQ_SYNCH_FRAME,                /* request */
 			      USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			      SQ905_PING, 0, gspca_dev->usb_buf, 1,
 			      SQ905_CMD_TIMEOUT);
 	if (ret < 0) {
 		err("%s: usb_control_msg failed 2 (%d)",
 			__func__, ret);
 		return ret;
 	}

 	return 0;
 }

 /*
  * Acknowledge the end of a frame - see warning on sq905_command.
  */
 static int sq905_ack_frame(struct gspca_dev *gspca_dev)
 {
 	int ret;

 	gspca_dev->usb_buf[0] = '\0';
 	ret = usb_control_msg(gspca_dev->dev,
 			      usb_sndctrlpipe(gspca_dev->dev, 0),
 			      USB_REQ_SYNCH_FRAME,                /* request */
 			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			      SQ905_READ_DONE, 0, gspca_dev->usb_buf, 1,
 			      SQ905_CMD_TIMEOUT);
 	if (ret < 0) {
 		err("%s: usb_control_msg failed (%d)", __func__, ret);
 		return ret;
 	}

 	return 0;
 }

 /*
  *  request and read a block of data - see warning on sq905_command.
  */
 static int
 sq905_read_data(struct gspca_dev *gspca_dev, u8 *data, int size, int need_lock)
 {
 	int ret;
 	int act_len;

 	gspca_dev->usb_buf[0] = '\0';
 	if (need_lock)
 		mutex_lock(&gspca_dev->usb_lock);
 	ret = usb_control_msg(gspca_dev->dev,
 			      usb_sndctrlpipe(gspca_dev->dev, 0),
 			      USB_REQ_SYNCH_FRAME,                /* request */
 			      USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			      SQ905_BULK_READ, size, gspca_dev->usb_buf,
 			      1, SQ905_CMD_TIMEOUT);
 	if (need_lock)
 		mutex_unlock(&gspca_dev->usb_lock);
 	if (ret < 0) {
 		err("%s: usb_control_msg failed (%d)", __func__, ret);
 		return ret;
 	}
 	ret = usb_bulk_msg(gspca_dev->dev,
 			   usb_rcvbulkpipe(gspca_dev->dev, 0x81),
 			   data, size, &act_len, SQ905_DATA_TIMEOUT);

 	/* successful, it returns 0, otherwise  negative */
 	if (ret < 0 || act_len != size) {
 		err("bulk read fail (%d) len %d/%d",
 			ret, act_len, size);
 		return -EIO;
 	}
 	return 0;
 }

 /* This function is called as a workqueue function and runs whenever the camera
  * is streaming data. Because it is a workqueue function it is allowed to sleep
  * so we can use synchronous USB calls. To avoid possible collisions with other
  * threads attempting to use the camera's USB interface we take the gspca
  * usb_lock when performing USB operations. In practice the only thing we need
  * to protect against is the usb_set_interface call that gspca makes during
  * stream_off as the camera doesn't provide any controls that the user could try
  * to change.
  */
 static void sq905_dostream(struct work_struct *work)
 {
 	struct sd *dev = container_of(work, struct sd, work_struct);
 	struct gspca_dev *gspca_dev = &dev->gspca_dev;
 	int bytes_left; /* bytes remaining in current frame. */
 	int data_len;   /* size to use for the next read. */
 	int header_read; /* true if we have already read the frame header. */
 	int packet_type;
 	int frame_sz;
 	int ret;
 	u8 *data;
 	u8 *buffer;

 	buffer = kmalloc(SQ905_MAX_TRANSFER, GFP_KERNEL | GFP_DMA);
 	if (!buffer) {
 		err("Couldn't allocate USB buffer");
 		goto quit_stream;
 	}

 	frame_sz = gspca_dev->cam.cam_mode[gspca_dev->curr_mode].sizeimage
 			+ FRAME_HEADER_LEN;

 	while (gspca_dev->present && gspca_dev->streaming) {
 		/* request some data and then read it until we have
 		 * a complete frame. */
 		bytes_left = frame_sz;
 		header_read = 0;

 		/* Note we do not check for gspca_dev->streaming here, as
 		   we must finish reading an entire frame, otherwise the
 		   next time we stream we start reading in the middle of a
 		   frame. */
 		while (bytes_left > 0 && gspca_dev->present) {
 			data_len = bytes_left > SQ905_MAX_TRANSFER ?
 				SQ905_MAX_TRANSFER : bytes_left;
 			ret = sq905_read_data(gspca_dev, buffer, data_len, 1);
 			if (ret < 0)
 				goto quit_stream;
 			PDEBUG(D_PACK,
 				"Got %d bytes out of %d for frame",
 				data_len, bytes_left);
 			bytes_left -= data_len;
 			data = buffer;
 			if (!header_read) {
 				packet_type = FIRST_PACKET;
 				/* The first 64 bytes of each frame are
 				 * a header full of FF 00 bytes */
 				data += FRAME_HEADER_LEN;
 				data_len -= FRAME_HEADER_LEN;
 				header_read = 1;
 			} else if (bytes_left == 0) {
 				packet_type = LAST_PACKET;
 			} else {
 				packet_type = INTER_PACKET;
 			}
 			gspca_frame_add(gspca_dev, packet_type,
 					data, data_len);
 			/* If entire frame fits in one packet we still
 			   need to add a LAST_PACKET */
 			if (packet_type == FIRST_PACKET &&
 			    bytes_left == 0)
 				gspca_frame_add(gspca_dev, LAST_PACKET,
 						NULL, 0);
 		}
 		if (gspca_dev->present) {
 			/* acknowledge the frame */
 			mutex_lock(&gspca_dev->usb_lock);
 			ret = sq905_ack_frame(gspca_dev);
 			mutex_unlock(&gspca_dev->usb_lock);
 			if (ret < 0)
 				goto quit_stream;
 		}
 	}
 quit_stream:
 	if (gspca_dev->present) {
 		mutex_lock(&gspca_dev->usb_lock);
 		sq905_command(gspca_dev, SQ905_CLEAR);
 		mutex_unlock(&gspca_dev->usb_lock);
 	}
 	kfree(buffer);
 }

 /* This function is called at probe time just before sd_init */
 static int sd_config(struct gspca_dev *gspca_dev,
 		const struct usb_device_id *id)
 {
 	struct cam *cam = &gspca_dev->cam;
 	struct sd *dev = (struct sd *) gspca_dev;

 	/* We don't use the buffer gspca allocates so make it small. */
 	cam->bulk = 1;
 	cam->bulk_size = 64;

 	INIT_WORK(&dev->work_struct, sq905_dostream);

 	return 0;
 }

 /* called on streamoff with alt==0 and on disconnect */
 /* the usb_lock is held at entry - restore on exit */
 static void sd_stop0(struct gspca_dev *gspca_dev)
 {
 	struct sd *dev = (struct sd *) gspca_dev;

 	/* wait for the work queue to terminate */
 	mutex_unlock(&gspca_dev->usb_lock);
 	/* This waits for sq905_dostream to finish */
 	destroy_workqueue(dev->work_thread);
 	dev->work_thread = NULL;
 	mutex_lock(&gspca_dev->usb_lock);
 }

 /* this function is called at probe and resume time */
 static int sd_init(struct gspca_dev *gspca_dev)
 {
 	u32 ident;
 	int ret;

 	/* connect to the camera and read
 	 * the model ID and process that and put it away.
 	 */
 	ret = sq905_command(gspca_dev, SQ905_CLEAR);
 	if (ret < 0)
 		return ret;
 	ret = sq905_command(gspca_dev, SQ905_ID);
 	if (ret < 0)
 		return ret;
 	ret = sq905_read_data(gspca_dev, gspca_dev->usb_buf, 4, 0);
 	if (ret < 0)
 		return ret;
 	/* usb_buf is allocated with kmalloc so is aligned.
 	 * Camera model number is the right way round if we assume this
 	 * reverse engineered ID is supposed to be big endian. */
 	ident = be32_to_cpup((__be32 *)gspca_dev->usb_buf);
 	ret = sq905_command(gspca_dev, SQ905_CLEAR);
 	if (ret < 0)
 		return ret;
 	PDEBUG(D_CONF, "SQ905 camera ID %08x detected", ident);
 	gspca_dev->cam.cam_mode = sq905_mode;
 	gspca_dev->cam.nmodes = ARRAY_SIZE(sq905_mode);
 	if (!(ident & SQ905_HIRES_MASK))
 		gspca_dev->cam.nmodes--;

 	if (ident & SQ905_ORIENTATION_MASK)
 		gspca_dev->cam.input_flags = V4L2_IN_ST_VFLIP;
 	else
 		gspca_dev->cam.input_flags = V4L2_IN_ST_VFLIP |
 					     V4L2_IN_ST_HFLIP;
 	return 0;
 }

 /* Set up for getting frames. */
 static int sd_start(struct gspca_dev *gspca_dev)
 {
 	struct sd *dev = (struct sd *) gspca_dev;
 	int ret;

 	/* "Open the shutter" and set size, to start capture */
 	switch (gspca_dev->curr_mode) {
 	default:
 /*	case 2: */
 		PDEBUG(D_STREAM, "Start streaming at high resolution");
 		ret = sq905_command(&dev->gspca_dev, SQ905_CAPTURE_HIGH);
 		break;
 	case 1:
 		PDEBUG(D_STREAM, "Start streaming at medium resolution");
 		ret = sq905_command(&dev->gspca_dev, SQ905_CAPTURE_MED);
 		break;
 	case 0:
 		PDEBUG(D_STREAM, "Start streaming at low resolution");
 		ret = sq905_command(&dev->gspca_dev, SQ905_CAPTURE_LOW);
 	}

 	if (ret < 0) {
 		PDEBUG(D_ERR, "Start streaming command failed");
 		return ret;
 	}
 	/* Start the workqueue function to do the streaming */
 	dev->work_thread = create_singlethread_workqueue(MODULE_NAME);
 	queue_work(dev->work_thread, &dev->work_struct);

 	return 0;
 }

 /* Table of supported USB devices */
 static const struct usb_device_id device_table[] = {
 	{USB_DEVICE(0x2770, 0x9120)},
 	{}
 };

 MODULE_DEVICE_TABLE(usb, device_table);

 /* sub-driver description */
 static const struct sd_desc sd_desc = {
 	.name   = MODULE_NAME,
 	.config = sd_config,
 	.init   = sd_init,
 	.start  = sd_start,
 	.stop0  = sd_stop0,
 };

 /* -- device connect -- */
 static int sd_probe(struct usb_interface *intf,
 		const struct usb_device_id *id)
 {
 	return gspca_dev_probe(intf, id,
 			&sd_desc,
 			sizeof(struct sd),
 			THIS_MODULE);
 }

 static struct usb_driver sd_driver = {
 	.name       = MODULE_NAME,
 	.id_table   = device_table,
 	.probe      = sd_probe,
 	.disconnect = gspca_disconnect,
 #ifdef CONFIG_PM
 	.suspend = gspca_suspend,
 	.resume  = gspca_resume,
 #endif
 };

 /* -- module insert / remove -- */
 static int __init sd_mod_init(void)
 {
 	return usb_register(&sd_driver);
 }

 static void __exit sd_mod_exit(void)
 {
 	usb_deregister(&sd_driver);
 }

 module_init(sd_mod_init);
 module_exit(sd_mod_exit);
	/*
	* SQ905 subdriver
	*
	* Copyright (C) 2008, 2009 Adam Baker and Theodore Kilgore
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* any later version.
	*
	* 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
	*/

	/*
	* History and Acknowledgments
	*
	* The original Linux driver for SQ905 based cameras was written by
	* Marcell Lengyel and furter developed by many other contributors
	* and is available from http://sourceforge.net/projects/sqcam/
	*
	* This driver takes advantage of the reverse engineering work done for
	* that driver and for libgphoto2 but shares no code with them.
	*
	* This driver has used as a base the finepix driver and other gspca
	* based drivers and may still contain code fragments taken from those
	* drivers.
	*/

	#define MODULE_NAME "sq905"

	#include <linux/workqueue.h>
	#include <linux/slab.h>
	#include "gspca.h"

	MODULE_AUTHOR("Adam Baker <linux@baker-net.org.uk>, "
	"Theodore Kilgore <kilgota@auburn.edu>");
	MODULE_DESCRIPTION("GSPCA/SQ905 USB Camera Driver");
	MODULE_LICENSE("GPL");

	/* Default timeouts, in ms */
	#define SQ905_CMD_TIMEOUT 500
	#define SQ905_DATA_TIMEOUT 1000

	/* Maximum transfer size to use. */
	#define SQ905_MAX_TRANSFER 0x8000
	#define FRAME_HEADER_LEN 64

	/* The known modes, or registers. These go in the "value" slot. */

	/* 00 is "none" obviously */

	#define SQ905_BULK_READ 0x03 /* precedes any bulk read */
	#define SQ905_COMMAND 0x06 /* precedes the command codes below */
	#define SQ905_PING 0x07 /* when reading an "idling" command */
	#define SQ905_READ_DONE 0xc0 /* ack bulk read completed */

	/* Any non-zero value in the bottom 2 bits of the 2nd byte of
	* the ID appears to indicate the camera can do 640*480. If the
	* LSB of that byte is set the image is just upside down, otherwise
	* it is rotated 180 degrees. */
	#define SQ905_HIRES_MASK 0x00000300
	#define SQ905_ORIENTATION_MASK 0x00000100

	/* Some command codes. These go in the "index" slot. */

	#define SQ905_ID 0xf0 /* asks for model string */
	#define SQ905_CONFIG 0x20 /* gets photo alloc. table, not used here */
	#define SQ905_DATA 0x30 /* accesses photo data, not used here */
	#define SQ905_CLEAR 0xa0 /* clear everything */
	#define SQ905_CAPTURE_LOW 0x60 /* Starts capture at 160x120 */
	#define SQ905_CAPTURE_MED 0x61 /* Starts capture at 320x240 */
	#define SQ905_CAPTURE_HIGH 0x62 /* Starts capture at 640x480 (some cams only) */
	/* note that the capture command also controls the output dimensions */

	/* Structure to hold all of our device specific stuff */
	struct sd {
	struct gspca_dev gspca_dev; /* !! must be the first item */

	/*
	* Driver stuff
	*/
	struct work_struct work_struct;
	struct workqueue_struct *work_thread;
	};

	static struct v4l2_pix_format sq905_mode[] = {
	{ 160, 120, V4L2_PIX_FMT_SBGGR8, V4L2_FIELD_NONE,
	.bytesperline = 160,
	.sizeimage = 160 * 120,
	.colorspace = V4L2_COLORSPACE_SRGB,
	.priv = 0},
	{ 320, 240, V4L2_PIX_FMT_SBGGR8, V4L2_FIELD_NONE,
	.bytesperline = 320,
	.sizeimage = 320 * 240,
	.colorspace = V4L2_COLORSPACE_SRGB,
	.priv = 0},
	{ 640, 480, V4L2_PIX_FMT_SBGGR8, V4L2_FIELD_NONE,
	.bytesperline = 640,
	.sizeimage = 640 * 480,
	.colorspace = V4L2_COLORSPACE_SRGB,
	.priv = 0}
	};

	/*
	* Send a command to the camera.
	*/
	static int sq905_command(struct gspca_dev *gspca_dev, u16 index)
	{
	int ret;

	gspca_dev->usb_buf[0] = '\0';
	ret = usb_control_msg(gspca_dev->dev,
	usb_sndctrlpipe(gspca_dev->dev, 0),
	USB_REQ_SYNCH_FRAME, /* request */
	USB_DIR_OUT \| USB_TYPE_VENDOR \| USB_RECIP_DEVICE,
	SQ905_COMMAND, index, gspca_dev->usb_buf, 1,
	SQ905_CMD_TIMEOUT);
	if (ret < 0) {
	err("%s: usb_control_msg failed (%d)",
	__func__, ret);
	return ret;
	}

	ret = usb_control_msg(gspca_dev->dev,
	usb_sndctrlpipe(gspca_dev->dev, 0),
	USB_REQ_SYNCH_FRAME, /* request */
	USB_DIR_IN \| USB_TYPE_VENDOR \| USB_RECIP_DEVICE,
	SQ905_PING, 0, gspca_dev->usb_buf, 1,
	SQ905_CMD_TIMEOUT);
	if (ret < 0) {
	err("%s: usb_control_msg failed 2 (%d)",
	__func__, ret);
	return ret;
	}

	return 0;
	}

	/*
	* Acknowledge the end of a frame - see warning on sq905_command.
	*/
	static int sq905_ack_frame(struct gspca_dev *gspca_dev)
	{
	int ret;

	gspca_dev->usb_buf[0] = '\0';
	ret = usb_control_msg(gspca_dev->dev,
	usb_sndctrlpipe(gspca_dev->dev, 0),
	USB_REQ_SYNCH_FRAME, /* request */
	USB_DIR_OUT \| USB_TYPE_VENDOR \| USB_RECIP_DEVICE,
	SQ905_READ_DONE, 0, gspca_dev->usb_buf, 1,
	SQ905_CMD_TIMEOUT);
	if (ret < 0) {
	err("%s: usb_control_msg failed (%d)", __func__, ret);
	return ret;
	}

	return 0;
	}

	/*
	* request and read a block of data - see warning on sq905_command.
	*/
	static int
	sq905_read_data(struct gspca_dev gspca_dev, u8 data, int size, int need_lock)
	{
	int ret;
	int act_len;

	gspca_dev->usb_buf[0] = '\0';
	if (need_lock)
	mutex_lock(&gspca_dev->usb_lock);
	ret = usb_control_msg(gspca_dev->dev,
	usb_sndctrlpipe(gspca_dev->dev, 0),
	USB_REQ_SYNCH_FRAME, /* request */
	USB_DIR_OUT \| USB_TYPE_VENDOR \| USB_RECIP_DEVICE,
	SQ905_BULK_READ, size, gspca_dev->usb_buf,
	1, SQ905_CMD_TIMEOUT);
	if (need_lock)
	mutex_unlock(&gspca_dev->usb_lock);
	if (ret < 0) {
	err("%s: usb_control_msg failed (%d)", __func__, ret);
	return ret;
	}
	ret = usb_bulk_msg(gspca_dev->dev,
	usb_rcvbulkpipe(gspca_dev->dev, 0x81),
	data, size, &act_len, SQ905_DATA_TIMEOUT);

	/* successful, it returns 0, otherwise negative */
	if (ret < 0 \|\| act_len != size) {
	err("bulk read fail (%d) len %d/%d",
	ret, act_len, size);
	return -EIO;
	}
	return 0;
	}

	/* This function is called as a workqueue function and runs whenever the camera
	* is streaming data. Because it is a workqueue function it is allowed to sleep
	* so we can use synchronous USB calls. To avoid possible collisions with other
	* threads attempting to use the camera's USB interface we take the gspca
	* usb_lock when performing USB operations. In practice the only thing we need
	* to protect against is the usb_set_interface call that gspca makes during
	* stream_off as the camera doesn't provide any controls that the user could try
	* to change.
	*/
	static void sq905_dostream(struct work_struct *work)
	{
	struct sd *dev = container_of(work, struct sd, work_struct);
	struct gspca_dev *gspca_dev = &dev->gspca_dev;
	int bytes_left; /* bytes remaining in current frame. */
	int data_len; /* size to use for the next read. */
	int header_read; /* true if we have already read the frame header. */
	int packet_type;
	int frame_sz;
	int ret;
	u8 *data;
	u8 *buffer;

	buffer = kmalloc(SQ905_MAX_TRANSFER, GFP_KERNEL \| GFP_DMA);
	if (!buffer) {
	err("Couldn't allocate USB buffer");
	goto quit_stream;
	}

	frame_sz = gspca_dev->cam.cam_mode[gspca_dev->curr_mode].sizeimage
	+ FRAME_HEADER_LEN;

	while (gspca_dev->present && gspca_dev->streaming) {
	/* request some data and then read it until we have
	* a complete frame. */
	bytes_left = frame_sz;
	header_read = 0;

	/* Note we do not check for gspca_dev->streaming here, as
	we must finish reading an entire frame, otherwise the
	next time we stream we start reading in the middle of a
	frame. */
	while (bytes_left > 0 && gspca_dev->present) {
	data_len = bytes_left > SQ905_MAX_TRANSFER ?
	SQ905_MAX_TRANSFER : bytes_left;
	ret = sq905_read_data(gspca_dev, buffer, data_len, 1);
	if (ret < 0)
	goto quit_stream;
	PDEBUG(D_PACK,
	"Got %d bytes out of %d for frame",
	data_len, bytes_left);
	bytes_left -= data_len;
	data = buffer;
	if (!header_read) {
	packet_type = FIRST_PACKET;
	/* The first 64 bytes of each frame are
	* a header full of FF 00 bytes */
	data += FRAME_HEADER_LEN;
	data_len -= FRAME_HEADER_LEN;
	header_read = 1;
	} else if (bytes_left == 0) {
	packet_type = LAST_PACKET;
	} else {
	packet_type = INTER_PACKET;
	}
	gspca_frame_add(gspca_dev, packet_type,
	data, data_len);
	/* If entire frame fits in one packet we still
	need to add a LAST_PACKET */
	if (packet_type == FIRST_PACKET &&
	bytes_left == 0)
	gspca_frame_add(gspca_dev, LAST_PACKET,
	NULL, 0);
	}
	if (gspca_dev->present) {
	/* acknowledge the frame */
	mutex_lock(&gspca_dev->usb_lock);
	ret = sq905_ack_frame(gspca_dev);
	mutex_unlock(&gspca_dev->usb_lock);
	if (ret < 0)
	goto quit_stream;
	}
	}
	quit_stream:
	if (gspca_dev->present) {
	mutex_lock(&gspca_dev->usb_lock);
	sq905_command(gspca_dev, SQ905_CLEAR);
	mutex_unlock(&gspca_dev->usb_lock);
	}
	kfree(buffer);
	}

	/* This function is called at probe time just before sd_init */
	static int sd_config(struct gspca_dev *gspca_dev,
	const struct usb_device_id *id)
	{
	struct cam *cam = &gspca_dev->cam;
	struct sd dev = (struct sd ) gspca_dev;

	/* We don't use the buffer gspca allocates so make it small. */
	cam->bulk = 1;
	cam->bulk_size = 64;

	INIT_WORK(&dev->work_struct, sq905_dostream);

	return 0;
	}

	/* called on streamoff with alt==0 and on disconnect */
	/* the usb_lock is held at entry - restore on exit */
	static void sd_stop0(struct gspca_dev *gspca_dev)
	{
	struct sd dev = (struct sd ) gspca_dev;

	/* wait for the work queue to terminate */
	mutex_unlock(&gspca_dev->usb_lock);
	/* This waits for sq905_dostream to finish */
	destroy_workqueue(dev->work_thread);
	dev->work_thread = NULL;
	mutex_lock(&gspca_dev->usb_lock);
	}

	/* this function is called at probe and resume time */
	static int sd_init(struct gspca_dev *gspca_dev)
	{
	u32 ident;
	int ret;

	/* connect to the camera and read
	* the model ID and process that and put it away.
	*/
	ret = sq905_command(gspca_dev, SQ905_CLEAR);
	if (ret < 0)
	return ret;
	ret = sq905_command(gspca_dev, SQ905_ID);
	if (ret < 0)
	return ret;
	ret = sq905_read_data(gspca_dev, gspca_dev->usb_buf, 4, 0);
	if (ret < 0)
	return ret;
	/* usb_buf is allocated with kmalloc so is aligned.
	* Camera model number is the right way round if we assume this
	* reverse engineered ID is supposed to be big endian. */
	ident = be32_to_cpup((__be32 *)gspca_dev->usb_buf);
	ret = sq905_command(gspca_dev, SQ905_CLEAR);
	if (ret < 0)
	return ret;
	PDEBUG(D_CONF, "SQ905 camera ID %08x detected", ident);
	gspca_dev->cam.cam_mode = sq905_mode;
	gspca_dev->cam.nmodes = ARRAY_SIZE(sq905_mode);
	if (!(ident & SQ905_HIRES_MASK))
	gspca_dev->cam.nmodes--;

	if (ident & SQ905_ORIENTATION_MASK)
	gspca_dev->cam.input_flags = V4L2_IN_ST_VFLIP;
	else
	gspca_dev->cam.input_flags = V4L2_IN_ST_VFLIP \|
	V4L2_IN_ST_HFLIP;
	return 0;
	}

	/* Set up for getting frames. */
	static int sd_start(struct gspca_dev *gspca_dev)
	{
	struct sd dev = (struct sd ) gspca_dev;
	int ret;

	/* "Open the shutter" and set size, to start capture */
	switch (gspca_dev->curr_mode) {
	default:
	/* case 2: */
	PDEBUG(D_STREAM, "Start streaming at high resolution");
	ret = sq905_command(&dev->gspca_dev, SQ905_CAPTURE_HIGH);
	break;
	case 1:
	PDEBUG(D_STREAM, "Start streaming at medium resolution");
	ret = sq905_command(&dev->gspca_dev, SQ905_CAPTURE_MED);
	break;
	case 0:
	PDEBUG(D_STREAM, "Start streaming at low resolution");
	ret = sq905_command(&dev->gspca_dev, SQ905_CAPTURE_LOW);
	}

	if (ret < 0) {
	PDEBUG(D_ERR, "Start streaming command failed");
	return ret;
	}
	/* Start the workqueue function to do the streaming */
	dev->work_thread = create_singlethread_workqueue(MODULE_NAME);
	queue_work(dev->work_thread, &dev->work_struct);

	return 0;
	}

	/* Table of supported USB devices */
	static const struct usb_device_id device_table[] = {
	{USB_DEVICE(0x2770, 0x9120)},
	{}
	};

	MODULE_DEVICE_TABLE(usb, device_table);

	/* sub-driver description */
	static const struct sd_desc sd_desc = {
	.name = MODULE_NAME,
	.config = sd_config,
	.init = sd_init,
	.start = sd_start,
	.stop0 = sd_stop0,
	};

	/* -- device connect -- */
	static int sd_probe(struct usb_interface *intf,
	const struct usb_device_id *id)
	{
	return gspca_dev_probe(intf, id,
	&sd_desc,
	sizeof(struct sd),
	THIS_MODULE);
	}

	static struct usb_driver sd_driver = {
	.name = MODULE_NAME,
	.id_table = device_table,
	.probe = sd_probe,
	.disconnect = gspca_disconnect,
	#ifdef CONFIG_PM
	.suspend = gspca_suspend,
	.resume = gspca_resume,
	#endif
	};

	/* -- module insert / remove -- */
	static int __init sd_mod_init(void)
	{
	return usb_register(&sd_driver);
	}

	static void __exit sd_mod_exit(void)
	{
	usb_deregister(&sd_driver);
	}

	module_init(sd_mod_init);
	module_exit(sd_mod_exit);