drivers/media/usb/stk1160/stk1160-video.c - maze/linux - Git at Google

 /*
  * STK1160 driver
  *
  * Copyright (C) 2012 Ezequiel Garcia
  * <elezegarcia--a.t--gmail.com>
  *
  * Based on Easycap driver by R.M. Thomas
  *	Copyright (C) 2010 R.M. Thomas
  *	<rmthomas--a.t--sciolus.org>
  *
  * 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
  * (at your option) 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.
  *
  */

 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/slab.h>
 #include <linux/ratelimit.h>

 #include "stk1160.h"

 static unsigned int debug;
 module_param(debug, int, 0644);
 MODULE_PARM_DESC(debug, "enable debug messages");

 static inline void print_err_status(struct stk1160 *dev,
 				     int packet, int status)
 {
 	char *errmsg = "Unknown";

 	switch (status) {
 	case -ENOENT:
 		errmsg = "unlinked synchronuously";
 		break;
 	case -ECONNRESET:
 		errmsg = "unlinked asynchronuously";
 		break;
 	case -ENOSR:
 		errmsg = "Buffer error (overrun)";
 		break;
 	case -EPIPE:
 		errmsg = "Stalled (device not responding)";
 		break;
 	case -EOVERFLOW:
 		errmsg = "Babble (bad cable?)";
 		break;
 	case -EPROTO:
 		errmsg = "Bit-stuff error (bad cable?)";
 		break;
 	case -EILSEQ:
 		errmsg = "CRC/Timeout (could be anything)";
 		break;
 	case -ETIME:
 		errmsg = "Device does not respond";
 		break;
 	}

 	if (packet < 0)
 		printk_ratelimited(KERN_WARNING "URB status %d [%s].\n",
 				status, errmsg);
 	else
 		printk_ratelimited(KERN_INFO "URB packet %d, status %d [%s].\n",
 			       packet, status, errmsg);
 }

 static inline
 struct stk1160_buffer *stk1160_next_buffer(struct stk1160 *dev)
 {
 	struct stk1160_buffer *buf = NULL;
 	unsigned long flags = 0;

 	/* Current buffer must be NULL when this functions gets called */
 	WARN_ON(dev->isoc_ctl.buf);

 	spin_lock_irqsave(&dev->buf_lock, flags);
 	if (!list_empty(&dev->avail_bufs)) {
 		buf = list_first_entry(&dev->avail_bufs,
 				struct stk1160_buffer, list);
 		list_del(&buf->list);
 	}
 	spin_unlock_irqrestore(&dev->buf_lock, flags);

 	return buf;
 }

 static inline
 void stk1160_buffer_done(struct stk1160 *dev)
 {
 	struct stk1160_buffer *buf = dev->isoc_ctl.buf;

 	dev->field_count++;

 	buf->vb.v4l2_buf.sequence = dev->field_count >> 1;
 	buf->vb.v4l2_buf.field = V4L2_FIELD_INTERLACED;
 	buf->vb.v4l2_buf.bytesused = buf->bytesused;
 	v4l2_get_timestamp(&buf->vb.v4l2_buf.timestamp);

 	vb2_set_plane_payload(&buf->vb, 0, buf->bytesused);
 	vb2_buffer_done(&buf->vb, VB2_BUF_STATE_DONE);

 	dev->isoc_ctl.buf = NULL;
 }

 static inline
 void stk1160_copy_video(struct stk1160 *dev, u8 *src, int len)
 {
 	int linesdone, lineoff, lencopy;
 	int bytesperline = dev->width * 2;
 	struct stk1160_buffer *buf = dev->isoc_ctl.buf;
 	u8 *dst = buf->mem;
 	int remain;

 	/*
 	 * TODO: These stk1160_dbg are very spammy!
 	 * We should 1) check why we are getting them
 	 * and 2) add ratelimit.
 	 *
 	 * UPDATE: One of the reasons (the only one?) for getting these
 	 * is incorrect standard (mismatch between expected and configured).
 	 * So perhaps, we could add a counter for errors. When the counter
 	 * reaches some value, we simply stop streaming.
 	 */

 	len -= 4;
 	src += 4;

 	remain = len;

 	linesdone = buf->pos / bytesperline;
 	lineoff = buf->pos % bytesperline; /* offset in current line */

 	if (!buf->odd)
 		dst += bytesperline;

 	/* Multiply linesdone by two, to take account of the other field */
 	dst += linesdone * bytesperline * 2 + lineoff;

 	/* Copy the remaining of current line */
 	if (remain < (bytesperline - lineoff))
 		lencopy = remain;
 	else
 		lencopy = bytesperline - lineoff;

 	/*
 	 * Check if we have enough space left in the buffer.
 	 * In that case, we force loop exit after copy.
 	 */
 	if (lencopy > buf->bytesused - buf->length) {
 		lencopy = buf->bytesused - buf->length;
 		remain = lencopy;
 	}

 	/* Check if the copy is done */
 	if (lencopy == 0 || remain == 0)
 		return;

 	/* Let the bug hunt begin! sanity checks! */
 	if (lencopy < 0) {
 		stk1160_dbg("copy skipped: negative lencopy\n");
 		return;
 	}

 	if ((unsigned long)dst + lencopy >
 		(unsigned long)buf->mem + buf->length) {
 		printk_ratelimited(KERN_WARNING "stk1160: buffer overflow detected\n");
 		return;
 	}

 	memcpy(dst, src, lencopy);

 	buf->bytesused += lencopy;
 	buf->pos += lencopy;
 	remain -= lencopy;

 	/* Copy current field line by line, interlacing with the other field */
 	while (remain > 0) {

 		dst += lencopy + bytesperline;
 		src += lencopy;

 		/* Copy one line at a time */
 		if (remain < bytesperline)
 			lencopy = remain;
 		else
 			lencopy = bytesperline;

 		/*
 		 * Check if we have enough space left in the buffer.
 		 * In that case, we force loop exit after copy.
 		 */
 		if (lencopy > buf->bytesused - buf->length) {
 			lencopy = buf->bytesused - buf->length;
 			remain = lencopy;
 		}

 		/* Check if the copy is done */
 		if (lencopy == 0 || remain == 0)
 			return;

 		if (lencopy < 0) {
 			printk_ratelimited(KERN_WARNING "stk1160: negative lencopy detected\n");
 			return;
 		}

 		if ((unsigned long)dst + lencopy >
 			(unsigned long)buf->mem + buf->length) {
 			printk_ratelimited(KERN_WARNING "stk1160: buffer overflow detected\n");
 			return;
 		}

 		memcpy(dst, src, lencopy);
 		remain -= lencopy;

 		buf->bytesused += lencopy;
 		buf->pos += lencopy;
 	}
 }

 /*
  * Controls the isoc copy of each urb packet
  */
 static void stk1160_process_isoc(struct stk1160 *dev, struct urb *urb)
 {
 	int i, len, status;
 	u8 *p;

 	if (!dev) {
 		stk1160_warn("%s called with null device\n", __func__);
 		return;
 	}

 	if (urb->status < 0) {
 		/* Print status and drop current packet (or field?) */
 		print_err_status(dev, -1, urb->status);
 		return;
 	}

 	for (i = 0; i < urb->number_of_packets; i++) {
 		status = urb->iso_frame_desc[i].status;
 		if (status < 0) {
 			print_err_status(dev, i, status);
 			continue;
 		}

 		/* Get packet actual length and pointer to data */
 		p = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
 		len = urb->iso_frame_desc[i].actual_length;

 		/* Empty packet */
 		if (len <= 4)
 			continue;

 		/*
 		 * An 8-byte packet sequence means end of field.
 		 * So if we don't have any packet, we start receiving one now
 		 * and if we do have a packet, then we are done with it.
 		 *
 		 * These end of field packets are always 0xc0 or 0x80,
 		 * but not always 8-byte long so we don't check packet length.
 		 */
 		if (p[0] == 0xc0) {

 			/*
 			 * If first byte is 0xc0 then we received
 			 * second field, and frame has ended.
 			 */
 			if (dev->isoc_ctl.buf != NULL)
 				stk1160_buffer_done(dev);

 			dev->isoc_ctl.buf = stk1160_next_buffer(dev);
 			if (dev->isoc_ctl.buf == NULL)
 				return;
 		}

 		/*
 		 * If we don't have a buffer here, then it means we
 		 * haven't found the start mark sequence.
 		 */
 		if (dev->isoc_ctl.buf == NULL)
 			continue;

 		if (p[0] == 0xc0 || p[0] == 0x80) {

 			/* We set next packet parity and
 			 * continue to get next one
 			 */
 			dev->isoc_ctl.buf->odd = *p & 0x40;
 			dev->isoc_ctl.buf->pos = 0;
 			continue;
 		}

 		stk1160_copy_video(dev, p, len);
 	}
 }


 /*
  * IRQ callback, called by URB callback
  */
 static void stk1160_isoc_irq(struct urb *urb)
 {
 	int i, rc;
 	struct stk1160 *dev = urb->context;

 	switch (urb->status) {
 	case 0:
 		break;
 	case -ECONNRESET:   /* kill */
 	case -ENOENT:
 	case -ESHUTDOWN:
 		/* TODO: check uvc driver: he frees the queue here */
 		return;
 	default:
 		stk1160_err("urb error! status %d\n", urb->status);
 		return;
 	}

 	stk1160_process_isoc(dev, urb);

 	/* Reset urb buffers */
 	for (i = 0; i < urb->number_of_packets; i++) {
 		urb->iso_frame_desc[i].status = 0;
 		urb->iso_frame_desc[i].actual_length = 0;
 	}

 	rc = usb_submit_urb(urb, GFP_ATOMIC);
 	if (rc)
 		stk1160_err("urb re-submit failed (%d)\n", rc);
 }

 /*
  * Cancel urbs
  * This function can't be called in atomic context
  */
 void stk1160_cancel_isoc(struct stk1160 *dev)
 {
 	int i, num_bufs = dev->isoc_ctl.num_bufs;

 	/*
 	 * This check is not necessary, but we add it
 	 * to avoid a spurious debug message
 	 */
 	if (!num_bufs)
 		return;

 	stk1160_dbg("killing %d urbs...\n", num_bufs);

 	for (i = 0; i < num_bufs; i++) {

 		/*
 		 * To kill urbs we can't be in atomic context.
 		 * We don't care for NULL pointer since
 		 * usb_kill_urb allows it.
 		 */
 		usb_kill_urb(dev->isoc_ctl.urb[i]);
 	}

 	stk1160_dbg("all urbs killed\n");
 }

 /*
  * Releases urb and transfer buffers
  * Obviusly, associated urb must be killed before releasing it.
  */
 void stk1160_free_isoc(struct stk1160 *dev)
 {
 	struct urb *urb;
 	int i, num_bufs = dev->isoc_ctl.num_bufs;

 	stk1160_dbg("freeing %d urb buffers...\n", num_bufs);

 	for (i = 0; i < num_bufs; i++) {

 		urb = dev->isoc_ctl.urb[i];
 		if (urb) {

 			if (dev->isoc_ctl.transfer_buffer[i]) {
 #ifndef CONFIG_DMA_NONCOHERENT
 				usb_free_coherent(dev->udev,
 					urb->transfer_buffer_length,
 					dev->isoc_ctl.transfer_buffer[i],
 					urb->transfer_dma);
 #else
 				kfree(dev->isoc_ctl.transfer_buffer[i]);
 #endif
 			}
 			usb_free_urb(urb);
 			dev->isoc_ctl.urb[i] = NULL;
 		}
 		dev->isoc_ctl.transfer_buffer[i] = NULL;
 	}

 	kfree(dev->isoc_ctl.urb);
 	kfree(dev->isoc_ctl.transfer_buffer);

 	dev->isoc_ctl.urb = NULL;
 	dev->isoc_ctl.transfer_buffer = NULL;
 	dev->isoc_ctl.num_bufs = 0;

 	stk1160_dbg("all urb buffers freed\n");
 }

 /*
  * Helper for cancelling and freeing urbs
  * This function can't be called in atomic context
  */
 void stk1160_uninit_isoc(struct stk1160 *dev)
 {
 	stk1160_cancel_isoc(dev);
 	stk1160_free_isoc(dev);
 }

 /*
  * Allocate URBs
  */
 int stk1160_alloc_isoc(struct stk1160 *dev)
 {
 	struct urb *urb;
 	int i, j, k, sb_size, max_packets, num_bufs;

 	/*
 	 * It may be necessary to release isoc here,
 	 * since isoc are only released on disconnection.
 	 * (see new_pkt_size flag)
 	 */
 	if (dev->isoc_ctl.num_bufs)
 		stk1160_uninit_isoc(dev);

 	stk1160_dbg("allocating urbs...\n");

 	num_bufs = STK1160_NUM_BUFS;
 	max_packets = STK1160_NUM_PACKETS;
 	sb_size = max_packets * dev->max_pkt_size;

 	dev->isoc_ctl.buf = NULL;
 	dev->isoc_ctl.max_pkt_size = dev->max_pkt_size;
 	dev->isoc_ctl.urb = kzalloc(sizeof(void *)*num_bufs, GFP_KERNEL);
 	if (!dev->isoc_ctl.urb) {
 		stk1160_err("out of memory for urb array\n");
 		return -ENOMEM;
 	}

 	dev->isoc_ctl.transfer_buffer = kzalloc(sizeof(void *)*num_bufs,
 					      GFP_KERNEL);
 	if (!dev->isoc_ctl.transfer_buffer) {
 		stk1160_err("out of memory for usb transfers\n");
 		kfree(dev->isoc_ctl.urb);
 		return -ENOMEM;
 	}

 	/* allocate urbs and transfer buffers */
 	for (i = 0; i < num_bufs; i++) {

 		urb = usb_alloc_urb(max_packets, GFP_KERNEL);
 		if (!urb) {
 			stk1160_err("cannot alloc urb[%d]\n", i);
 			goto free_i_bufs;
 		}
 		dev->isoc_ctl.urb[i] = urb;

 #ifndef CONFIG_DMA_NONCOHERENT
 		dev->isoc_ctl.transfer_buffer[i] = usb_alloc_coherent(dev->udev,
 			sb_size, GFP_KERNEL, &urb->transfer_dma);
 #else
 		dev->isoc_ctl.transfer_buffer[i] = kmalloc(sb_size, GFP_KERNEL);
 #endif
 		if (!dev->isoc_ctl.transfer_buffer[i]) {
 			stk1160_err("cannot alloc %d bytes for tx[%d] buffer\n",
 				sb_size, i);

 			/* Not enough transfer buffers, so just give up */
 			if (i < STK1160_MIN_BUFS)
 				goto free_i_bufs;
 			goto nomore_tx_bufs;
 		}
 		memset(dev->isoc_ctl.transfer_buffer[i], 0, sb_size);

 		/*
 		 * FIXME: Where can I get the endpoint?
 		 */
 		urb->dev = dev->udev;
 		urb->pipe = usb_rcvisocpipe(dev->udev, STK1160_EP_VIDEO);
 		urb->transfer_buffer = dev->isoc_ctl.transfer_buffer[i];
 		urb->transfer_buffer_length = sb_size;
 		urb->complete = stk1160_isoc_irq;
 		urb->context = dev;
 		urb->interval = 1;
 		urb->start_frame = 0;
 		urb->number_of_packets = max_packets;
 #ifndef CONFIG_DMA_NONCOHERENT
 		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
 #else
 		urb->transfer_flags = URB_ISO_ASAP;
 #endif

 		k = 0;
 		for (j = 0; j < max_packets; j++) {
 			urb->iso_frame_desc[j].offset = k;
 			urb->iso_frame_desc[j].length =
 					dev->isoc_ctl.max_pkt_size;
 			k += dev->isoc_ctl.max_pkt_size;
 		}
 	}

 	stk1160_dbg("%d urbs allocated\n", num_bufs);

 	/* At last we can say we have some buffers */
 	dev->isoc_ctl.num_bufs = num_bufs;

 	return 0;

 nomore_tx_bufs:
 	/*
 	 * Failed to allocate desired buffer count. However, we may have
 	 * enough to work fine, so we just free the extra urb,
 	 * store the allocated count and keep going, fingers crossed!
 	 */
 	usb_free_urb(dev->isoc_ctl.urb[i]);
 	dev->isoc_ctl.urb[i] = NULL;

 	stk1160_warn("%d urbs allocated. Trying to continue...\n", i - 1);

 	dev->isoc_ctl.num_bufs = i - 1;

 	return 0;

 free_i_bufs:
 	/* Save the allocated buffers so far, so we can properly free them */
 	dev->isoc_ctl.num_bufs = i+1;
 	stk1160_free_isoc(dev);
 	return -ENOMEM;
 }
	/*
	* STK1160 driver
	*
	* Copyright (C) 2012 Ezequiel Garcia
	* <elezegarcia--a.t--gmail.com>
	*
	* Based on Easycap driver by R.M. Thomas
	* Copyright (C) 2010 R.M. Thomas
	* <rmthomas--a.t--sciolus.org>
	*
	* 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
	* (at your option) 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.
	*
	*/

	#include <linux/module.h>
	#include <linux/usb.h>
	#include <linux/slab.h>
	#include <linux/ratelimit.h>

	#include "stk1160.h"

	static unsigned int debug;
	module_param(debug, int, 0644);
	MODULE_PARM_DESC(debug, "enable debug messages");

	static inline void print_err_status(struct stk1160 *dev,
	int packet, int status)
	{
	char *errmsg = "Unknown";

	switch (status) {
	case -ENOENT:
	errmsg = "unlinked synchronuously";
	break;
	case -ECONNRESET:
	errmsg = "unlinked asynchronuously";
	break;
	case -ENOSR:
	errmsg = "Buffer error (overrun)";
	break;
	case -EPIPE:
	errmsg = "Stalled (device not responding)";
	break;
	case -EOVERFLOW:
	errmsg = "Babble (bad cable?)";
	break;
	case -EPROTO:
	errmsg = "Bit-stuff error (bad cable?)";
	break;
	case -EILSEQ:
	errmsg = "CRC/Timeout (could be anything)";
	break;
	case -ETIME:
	errmsg = "Device does not respond";
	break;
	}

	if (packet < 0)
	printk_ratelimited(KERN_WARNING "URB status %d [%s].\n",
	status, errmsg);
	else
	printk_ratelimited(KERN_INFO "URB packet %d, status %d [%s].\n",
	packet, status, errmsg);
	}

	static inline
	struct stk1160_buffer stk1160_next_buffer(struct stk1160 dev)
	{
	struct stk1160_buffer *buf = NULL;
	unsigned long flags = 0;

	/* Current buffer must be NULL when this functions gets called */
	WARN_ON(dev->isoc_ctl.buf);

	spin_lock_irqsave(&dev->buf_lock, flags);
	if (!list_empty(&dev->avail_bufs)) {
	buf = list_first_entry(&dev->avail_bufs,
	struct stk1160_buffer, list);
	list_del(&buf->list);
	}
	spin_unlock_irqrestore(&dev->buf_lock, flags);

	return buf;
	}

	static inline
	void stk1160_buffer_done(struct stk1160 *dev)
	{
	struct stk1160_buffer *buf = dev->isoc_ctl.buf;

	dev->field_count++;

	buf->vb.v4l2_buf.sequence = dev->field_count >> 1;
	buf->vb.v4l2_buf.field = V4L2_FIELD_INTERLACED;
	buf->vb.v4l2_buf.bytesused = buf->bytesused;
	v4l2_get_timestamp(&buf->vb.v4l2_buf.timestamp);

	vb2_set_plane_payload(&buf->vb, 0, buf->bytesused);
	vb2_buffer_done(&buf->vb, VB2_BUF_STATE_DONE);

	dev->isoc_ctl.buf = NULL;
	}

	static inline
	void stk1160_copy_video(struct stk1160 dev, u8 src, int len)
	{
	int linesdone, lineoff, lencopy;
	int bytesperline = dev->width * 2;
	struct stk1160_buffer *buf = dev->isoc_ctl.buf;
	u8 *dst = buf->mem;
	int remain;

	/*
	* TODO: These stk1160_dbg are very spammy!
	* We should 1) check why we are getting them
	* and 2) add ratelimit.
	*
	* UPDATE: One of the reasons (the only one?) for getting these
	* is incorrect standard (mismatch between expected and configured).
	* So perhaps, we could add a counter for errors. When the counter
	* reaches some value, we simply stop streaming.
	*/

	len -= 4;
	src += 4;

	remain = len;

	linesdone = buf->pos / bytesperline;
	lineoff = buf->pos % bytesperline; /* offset in current line */

	if (!buf->odd)
	dst += bytesperline;

	/* Multiply linesdone by two, to take account of the other field */
	dst += linesdone * bytesperline * 2 + lineoff;

	/* Copy the remaining of current line */
	if (remain < (bytesperline - lineoff))
	lencopy = remain;
	else
	lencopy = bytesperline - lineoff;

	/*
	* Check if we have enough space left in the buffer.
	* In that case, we force loop exit after copy.
	*/
	if (lencopy > buf->bytesused - buf->length) {
	lencopy = buf->bytesused - buf->length;
	remain = lencopy;
	}

	/* Check if the copy is done */
	if (lencopy == 0 \|\| remain == 0)
	return;

	/* Let the bug hunt begin! sanity checks! */
	if (lencopy < 0) {
	stk1160_dbg("copy skipped: negative lencopy\n");
	return;
	}

	if ((unsigned long)dst + lencopy >
	(unsigned long)buf->mem + buf->length) {
	printk_ratelimited(KERN_WARNING "stk1160: buffer overflow detected\n");
	return;
	}

	memcpy(dst, src, lencopy);

	buf->bytesused += lencopy;
	buf->pos += lencopy;
	remain -= lencopy;

	/* Copy current field line by line, interlacing with the other field */
	while (remain > 0) {

	dst += lencopy + bytesperline;
	src += lencopy;

	/* Copy one line at a time */
	if (remain < bytesperline)
	lencopy = remain;
	else
	lencopy = bytesperline;

	/*
	* Check if we have enough space left in the buffer.
	* In that case, we force loop exit after copy.
	*/
	if (lencopy > buf->bytesused - buf->length) {
	lencopy = buf->bytesused - buf->length;
	remain = lencopy;
	}

	/* Check if the copy is done */
	if (lencopy == 0 \|\| remain == 0)
	return;

	if (lencopy < 0) {
	printk_ratelimited(KERN_WARNING "stk1160: negative lencopy detected\n");
	return;
	}

	if ((unsigned long)dst + lencopy >
	(unsigned long)buf->mem + buf->length) {
	printk_ratelimited(KERN_WARNING "stk1160: buffer overflow detected\n");
	return;
	}

	memcpy(dst, src, lencopy);
	remain -= lencopy;

	buf->bytesused += lencopy;
	buf->pos += lencopy;
	}
	}

	/*
	* Controls the isoc copy of each urb packet
	*/
	static void stk1160_process_isoc(struct stk1160 dev, struct urb urb)
	{
	int i, len, status;
	u8 *p;

	if (!dev) {
	stk1160_warn("%s called with null device\n", __func__);
	return;
	}

	if (urb->status < 0) {
	/* Print status and drop current packet (or field?) */
	print_err_status(dev, -1, urb->status);
	return;
	}

	for (i = 0; i < urb->number_of_packets; i++) {
	status = urb->iso_frame_desc[i].status;
	if (status < 0) {
	print_err_status(dev, i, status);
	continue;
	}

	/* Get packet actual length and pointer to data */
	p = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
	len = urb->iso_frame_desc[i].actual_length;

	/* Empty packet */
	if (len <= 4)
	continue;

	/*
	* An 8-byte packet sequence means end of field.
	* So if we don't have any packet, we start receiving one now
	* and if we do have a packet, then we are done with it.
	*
	* These end of field packets are always 0xc0 or 0x80,
	* but not always 8-byte long so we don't check packet length.
	*/
	if (p[0] == 0xc0) {

	/*
	* If first byte is 0xc0 then we received
	* second field, and frame has ended.
	*/
	if (dev->isoc_ctl.buf != NULL)
	stk1160_buffer_done(dev);

	dev->isoc_ctl.buf = stk1160_next_buffer(dev);
	if (dev->isoc_ctl.buf == NULL)
	return;
	}

	/*
	* If we don't have a buffer here, then it means we
	* haven't found the start mark sequence.
	*/
	if (dev->isoc_ctl.buf == NULL)
	continue;

	if (p[0] == 0xc0 \|\| p[0] == 0x80) {

	/* We set next packet parity and
	* continue to get next one
	*/
	dev->isoc_ctl.buf->odd = *p & 0x40;
	dev->isoc_ctl.buf->pos = 0;
	continue;
	}

	stk1160_copy_video(dev, p, len);
	}
	}


	/*
	* IRQ callback, called by URB callback
	*/
	static void stk1160_isoc_irq(struct urb *urb)
	{
	int i, rc;
	struct stk1160 *dev = urb->context;

	switch (urb->status) {
	case 0:
	break;
	case -ECONNRESET: /* kill */
	case -ENOENT:
	case -ESHUTDOWN:
	/* TODO: check uvc driver: he frees the queue here */
	return;
	default:
	stk1160_err("urb error! status %d\n", urb->status);
	return;
	}

	stk1160_process_isoc(dev, urb);

	/* Reset urb buffers */
	for (i = 0; i < urb->number_of_packets; i++) {
	urb->iso_frame_desc[i].status = 0;
	urb->iso_frame_desc[i].actual_length = 0;
	}

	rc = usb_submit_urb(urb, GFP_ATOMIC);
	if (rc)
	stk1160_err("urb re-submit failed (%d)\n", rc);
	}

	/*
	* Cancel urbs
	* This function can't be called in atomic context
	*/
	void stk1160_cancel_isoc(struct stk1160 *dev)
	{
	int i, num_bufs = dev->isoc_ctl.num_bufs;

	/*
	* This check is not necessary, but we add it
	* to avoid a spurious debug message
	*/
	if (!num_bufs)
	return;

	stk1160_dbg("killing %d urbs...\n", num_bufs);

	for (i = 0; i < num_bufs; i++) {

	/*
	* To kill urbs we can't be in atomic context.
	* We don't care for NULL pointer since
	* usb_kill_urb allows it.
	*/
	usb_kill_urb(dev->isoc_ctl.urb[i]);
	}

	stk1160_dbg("all urbs killed\n");
	}

	/*
	* Releases urb and transfer buffers
	* Obviusly, associated urb must be killed before releasing it.
	*/
	void stk1160_free_isoc(struct stk1160 *dev)
	{
	struct urb *urb;
	int i, num_bufs = dev->isoc_ctl.num_bufs;

	stk1160_dbg("freeing %d urb buffers...\n", num_bufs);

	for (i = 0; i < num_bufs; i++) {

	urb = dev->isoc_ctl.urb[i];
	if (urb) {

	if (dev->isoc_ctl.transfer_buffer[i]) {
	#ifndef CONFIG_DMA_NONCOHERENT
	usb_free_coherent(dev->udev,
	urb->transfer_buffer_length,
	dev->isoc_ctl.transfer_buffer[i],
	urb->transfer_dma);
	#else
	kfree(dev->isoc_ctl.transfer_buffer[i]);
	#endif
	}
	usb_free_urb(urb);
	dev->isoc_ctl.urb[i] = NULL;
	}
	dev->isoc_ctl.transfer_buffer[i] = NULL;
	}

	kfree(dev->isoc_ctl.urb);
	kfree(dev->isoc_ctl.transfer_buffer);

	dev->isoc_ctl.urb = NULL;
	dev->isoc_ctl.transfer_buffer = NULL;
	dev->isoc_ctl.num_bufs = 0;

	stk1160_dbg("all urb buffers freed\n");
	}

	/*
	* Helper for cancelling and freeing urbs
	* This function can't be called in atomic context
	*/
	void stk1160_uninit_isoc(struct stk1160 *dev)
	{
	stk1160_cancel_isoc(dev);
	stk1160_free_isoc(dev);
	}

	/*
	* Allocate URBs
	*/
	int stk1160_alloc_isoc(struct stk1160 *dev)
	{
	struct urb *urb;
	int i, j, k, sb_size, max_packets, num_bufs;

	/*
	* It may be necessary to release isoc here,
	* since isoc are only released on disconnection.
	* (see new_pkt_size flag)
	*/
	if (dev->isoc_ctl.num_bufs)
	stk1160_uninit_isoc(dev);

	stk1160_dbg("allocating urbs...\n");

	num_bufs = STK1160_NUM_BUFS;
	max_packets = STK1160_NUM_PACKETS;
	sb_size = max_packets * dev->max_pkt_size;

	dev->isoc_ctl.buf = NULL;
	dev->isoc_ctl.max_pkt_size = dev->max_pkt_size;
	dev->isoc_ctl.urb = kzalloc(sizeof(void )num_bufs, GFP_KERNEL);
	if (!dev->isoc_ctl.urb) {
	stk1160_err("out of memory for urb array\n");
	return -ENOMEM;
	}

	dev->isoc_ctl.transfer_buffer = kzalloc(sizeof(void )num_bufs,
	GFP_KERNEL);
	if (!dev->isoc_ctl.transfer_buffer) {
	stk1160_err("out of memory for usb transfers\n");
	kfree(dev->isoc_ctl.urb);
	return -ENOMEM;
	}

	/* allocate urbs and transfer buffers */
	for (i = 0; i < num_bufs; i++) {

	urb = usb_alloc_urb(max_packets, GFP_KERNEL);
	if (!urb) {
	stk1160_err("cannot alloc urb[%d]\n", i);
	goto free_i_bufs;
	}
	dev->isoc_ctl.urb[i] = urb;

	#ifndef CONFIG_DMA_NONCOHERENT
	dev->isoc_ctl.transfer_buffer[i] = usb_alloc_coherent(dev->udev,
	sb_size, GFP_KERNEL, &urb->transfer_dma);
	#else
	dev->isoc_ctl.transfer_buffer[i] = kmalloc(sb_size, GFP_KERNEL);
	#endif
	if (!dev->isoc_ctl.transfer_buffer[i]) {
	stk1160_err("cannot alloc %d bytes for tx[%d] buffer\n",
	sb_size, i);

	/* Not enough transfer buffers, so just give up */
	if (i < STK1160_MIN_BUFS)
	goto free_i_bufs;
	goto nomore_tx_bufs;
	}
	memset(dev->isoc_ctl.transfer_buffer[i], 0, sb_size);

	/*
	* FIXME: Where can I get the endpoint?
	*/
	urb->dev = dev->udev;
	urb->pipe = usb_rcvisocpipe(dev->udev, STK1160_EP_VIDEO);
	urb->transfer_buffer = dev->isoc_ctl.transfer_buffer[i];
	urb->transfer_buffer_length = sb_size;
	urb->complete = stk1160_isoc_irq;
	urb->context = dev;
	urb->interval = 1;
	urb->start_frame = 0;
	urb->number_of_packets = max_packets;
	#ifndef CONFIG_DMA_NONCOHERENT
	urb->transfer_flags = URB_ISO_ASAP \| URB_NO_TRANSFER_DMA_MAP;
	#else
	urb->transfer_flags = URB_ISO_ASAP;
	#endif

	k = 0;
	for (j = 0; j < max_packets; j++) {
	urb->iso_frame_desc[j].offset = k;
	urb->iso_frame_desc[j].length =
	dev->isoc_ctl.max_pkt_size;
	k += dev->isoc_ctl.max_pkt_size;
	}
	}

	stk1160_dbg("%d urbs allocated\n", num_bufs);

	/* At last we can say we have some buffers */
	dev->isoc_ctl.num_bufs = num_bufs;

	return 0;

	nomore_tx_bufs:
	/*
	* Failed to allocate desired buffer count. However, we may have
	* enough to work fine, so we just free the extra urb,
	* store the allocated count and keep going, fingers crossed!
	*/
	usb_free_urb(dev->isoc_ctl.urb[i]);
	dev->isoc_ctl.urb[i] = NULL;

	stk1160_warn("%d urbs allocated. Trying to continue...\n", i - 1);

	dev->isoc_ctl.num_bufs = i - 1;

	return 0;

	free_i_bufs:
	/* Save the allocated buffers so far, so we can properly free them */
	dev->isoc_ctl.num_bufs = i+1;
	stk1160_free_isoc(dev);
	return -ENOMEM;
	}