drivers/usb/gadget/uvc_queue.c - maze/linux - Git at Google

 /*
  *	uvc_queue.c  --  USB Video Class driver - Buffers management
  *
  *	Copyright (C) 2005-2010
  *	    Laurent Pinchart (laurent.pinchart@ideasonboard.com)
  *
  *	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.
  */

 #include <linux/atomic.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/videodev2.h>
 #include <linux/vmalloc.h>
 #include <linux/wait.h>

 #include <media/videobuf2-vmalloc.h>

 #include "uvc.h"

 /* ------------------------------------------------------------------------
  * Video buffers queue management.
  *
  * Video queues is initialized by uvc_queue_init(). The function performs
  * basic initialization of the uvc_video_queue struct and never fails.
  *
  * Video buffers are managed by videobuf2. The driver uses a mutex to protect
  * the videobuf2 queue operations by serializing calls to videobuf2 and a
  * spinlock to protect the IRQ queue that holds the buffers to be processed by
  * the driver.
  */

 /* -----------------------------------------------------------------------------
  * videobuf2 queue operations
  */

 static int uvc_queue_setup(struct vb2_queue *vq, const struct v4l2_format *fmt,
 			   unsigned int *nbuffers, unsigned int *nplanes,
 			   unsigned int sizes[], void *alloc_ctxs[])
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
 	struct uvc_video *video = container_of(queue, struct uvc_video, queue);

 	if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
 		*nbuffers = UVC_MAX_VIDEO_BUFFERS;

 	*nplanes = 1;

 	sizes[0] = video->imagesize;

 	return 0;
 }

 static int uvc_buffer_prepare(struct vb2_buffer *vb)
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
 	struct uvc_buffer *buf = container_of(vb, struct uvc_buffer, buf);

 	if (vb->v4l2_buf.type == V4L2_BUF_TYPE_VIDEO_OUTPUT &&
 	    vb2_get_plane_payload(vb, 0) > vb2_plane_size(vb, 0)) {
 		uvc_trace(UVC_TRACE_CAPTURE, "[E] Bytes used out of bounds.\n");
 		return -EINVAL;
 	}

 	if (unlikely(queue->flags & UVC_QUEUE_DISCONNECTED))
 		return -ENODEV;

 	buf->state = UVC_BUF_STATE_QUEUED;
 	buf->mem = vb2_plane_vaddr(vb, 0);
 	buf->length = vb2_plane_size(vb, 0);
 	if (vb->v4l2_buf.type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
 		buf->bytesused = 0;
 	else
 		buf->bytesused = vb2_get_plane_payload(vb, 0);

 	return 0;
 }

 static void uvc_buffer_queue(struct vb2_buffer *vb)
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
 	struct uvc_buffer *buf = container_of(vb, struct uvc_buffer, buf);
 	unsigned long flags;

 	spin_lock_irqsave(&queue->irqlock, flags);

 	if (likely(!(queue->flags & UVC_QUEUE_DISCONNECTED))) {
 		list_add_tail(&buf->queue, &queue->irqqueue);
 	} else {
 		/* If the device is disconnected return the buffer to userspace
 		 * directly. The next QBUF call will fail with -ENODEV.
 		 */
 		buf->state = UVC_BUF_STATE_ERROR;
 		vb2_buffer_done(&buf->buf, VB2_BUF_STATE_ERROR);
 	}

 	spin_unlock_irqrestore(&queue->irqlock, flags);
 }

 static struct vb2_ops uvc_queue_qops = {
 	.queue_setup = uvc_queue_setup,
 	.buf_prepare = uvc_buffer_prepare,
 	.buf_queue = uvc_buffer_queue,
 };

 static int uvc_queue_init(struct uvc_video_queue *queue,
 			  enum v4l2_buf_type type)
 {
 	int ret;

 	queue->queue.type = type;
 	queue->queue.io_modes = VB2_MMAP | VB2_USERPTR;
 	queue->queue.drv_priv = queue;
 	queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
 	queue->queue.ops = &uvc_queue_qops;
 	queue->queue.mem_ops = &vb2_vmalloc_memops;
 	ret = vb2_queue_init(&queue->queue);
 	if (ret)
 		return ret;

 	mutex_init(&queue->mutex);
 	spin_lock_init(&queue->irqlock);
 	INIT_LIST_HEAD(&queue->irqqueue);
 	queue->flags = 0;

 	return 0;
 }

 /*
  * Free the video buffers.
  */
 static void uvc_free_buffers(struct uvc_video_queue *queue)
 {
 	mutex_lock(&queue->mutex);
 	vb2_queue_release(&queue->queue);
 	mutex_unlock(&queue->mutex);
 }

 /*
  * Allocate the video buffers.
  */
 static int uvc_alloc_buffers(struct uvc_video_queue *queue,
 			     struct v4l2_requestbuffers *rb)
 {
 	int ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_reqbufs(&queue->queue, rb);
 	mutex_unlock(&queue->mutex);

 	return ret ? ret : rb->count;
 }

 static int uvc_query_buffer(struct uvc_video_queue *queue,
 			    struct v4l2_buffer *buf)
 {
 	int ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_querybuf(&queue->queue, buf);
 	mutex_unlock(&queue->mutex);

 	return ret;
 }

 static int uvc_queue_buffer(struct uvc_video_queue *queue,
 			    struct v4l2_buffer *buf)
 {
 	unsigned long flags;
 	int ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_qbuf(&queue->queue, buf);
 	spin_lock_irqsave(&queue->irqlock, flags);
 	ret = (queue->flags & UVC_QUEUE_PAUSED) != 0;
 	queue->flags &= ~UVC_QUEUE_PAUSED;
 	spin_unlock_irqrestore(&queue->irqlock, flags);
 	mutex_unlock(&queue->mutex);

 	return ret;
 }

 /*
  * Dequeue a video buffer. If nonblocking is false, block until a buffer is
  * available.
  */
 static int uvc_dequeue_buffer(struct uvc_video_queue *queue,
 			      struct v4l2_buffer *buf, int nonblocking)
 {
 	int ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_dqbuf(&queue->queue, buf, nonblocking);
 	mutex_unlock(&queue->mutex);

 	return ret;
 }

 /*
  * Poll the video queue.
  *
  * This function implements video queue polling and is intended to be used by
  * the device poll handler.
  */
 static unsigned int uvc_queue_poll(struct uvc_video_queue *queue,
 				   struct file *file, poll_table *wait)
 {
 	unsigned int ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_poll(&queue->queue, file, wait);
 	mutex_unlock(&queue->mutex);

 	return ret;
 }

 static int uvc_queue_mmap(struct uvc_video_queue *queue,
 			  struct vm_area_struct *vma)
 {
 	int ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_mmap(&queue->queue, vma);
 	mutex_unlock(&queue->mutex);

 	return ret;
 }

 #ifndef CONFIG_MMU
 /*
  * Get unmapped area.
  *
  * NO-MMU arch need this function to make mmap() work correctly.
  */
 static unsigned long uvc_queue_get_unmapped_area(struct uvc_video_queue *queue,
 		unsigned long pgoff)
 {
 	unsigned long ret;

 	mutex_lock(&queue->mutex);
 	ret = vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
 	mutex_unlock(&queue->mutex);
 	return ret;
 }
 #endif

 /*
  * Cancel the video buffers queue.
  *
  * Cancelling the queue marks all buffers on the irq queue as erroneous,
  * wakes them up and removes them from the queue.
  *
  * If the disconnect parameter is set, further calls to uvc_queue_buffer will
  * fail with -ENODEV.
  *
  * This function acquires the irq spinlock and can be called from interrupt
  * context.
  */
 static void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect)
 {
 	struct uvc_buffer *buf;
 	unsigned long flags;

 	spin_lock_irqsave(&queue->irqlock, flags);
 	while (!list_empty(&queue->irqqueue)) {
 		buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
 				       queue);
 		list_del(&buf->queue);
 		buf->state = UVC_BUF_STATE_ERROR;
 		vb2_buffer_done(&buf->buf, VB2_BUF_STATE_ERROR);
 	}
 	/* This must be protected by the irqlock spinlock to avoid race
 	 * conditions between uvc_queue_buffer and the disconnection event that
 	 * could result in an interruptible wait in uvc_dequeue_buffer. Do not
 	 * blindly replace this logic by checking for the UVC_DEV_DISCONNECTED
 	 * state outside the queue code.
 	 */
 	if (disconnect)
 		queue->flags |= UVC_QUEUE_DISCONNECTED;
 	spin_unlock_irqrestore(&queue->irqlock, flags);
 }

 /*
  * Enable or disable the video buffers queue.
  *
  * The queue must be enabled before starting video acquisition and must be
  * disabled after stopping it. This ensures that the video buffers queue
  * state can be properly initialized before buffers are accessed from the
  * interrupt handler.
  *
  * Enabling the video queue initializes parameters (such as sequence number,
  * sync pattern, ...). If the queue is already enabled, return -EBUSY.
  *
  * Disabling the video queue cancels the queue and removes all buffers from
  * the main queue.
  *
  * This function can't be called from interrupt context. Use
  * uvc_queue_cancel() instead.
  */
 static int uvc_queue_enable(struct uvc_video_queue *queue, int enable)
 {
 	unsigned long flags;
 	int ret = 0;

 	mutex_lock(&queue->mutex);
 	if (enable) {
 		ret = vb2_streamon(&queue->queue, queue->queue.type);
 		if (ret < 0)
 			goto done;

 		queue->sequence = 0;
 		queue->buf_used = 0;
 	} else {
 		ret = vb2_streamoff(&queue->queue, queue->queue.type);
 		if (ret < 0)
 			goto done;

 		spin_lock_irqsave(&queue->irqlock, flags);
 		INIT_LIST_HEAD(&queue->irqqueue);

 		/*
 		 * FIXME: We need to clear the DISCONNECTED flag to ensure that
 		 * applications will be able to queue buffers for the next
 		 * streaming run. However, clearing it here doesn't guarantee
 		 * that the device will be reconnected in the meantime.
 		 */
 		queue->flags &= ~UVC_QUEUE_DISCONNECTED;
 		spin_unlock_irqrestore(&queue->irqlock, flags);
 	}

 done:
 	mutex_unlock(&queue->mutex);
 	return ret;
 }

 /* called with &queue_irqlock held.. */
 static struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
 						struct uvc_buffer *buf)
 {
 	struct uvc_buffer *nextbuf;

 	if ((queue->flags & UVC_QUEUE_DROP_INCOMPLETE) &&
 	     buf->length != buf->bytesused) {
 		buf->state = UVC_BUF_STATE_QUEUED;
 		vb2_set_plane_payload(&buf->buf, 0, 0);
 		return buf;
 	}

 	list_del(&buf->queue);
 	if (!list_empty(&queue->irqqueue))
 		nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
 					   queue);
 	else
 		nextbuf = NULL;

 	/*
 	 * FIXME: with videobuf2, the sequence number or timestamp fields
 	 * are valid only for video capture devices and the UVC gadget usually
 	 * is a video output device. Keeping these until the specs are clear on
 	 * this aspect.
 	 */
 	buf->buf.v4l2_buf.sequence = queue->sequence++;
 	do_gettimeofday(&buf->buf.v4l2_buf.timestamp);

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

 	return nextbuf;
 }

 static struct uvc_buffer *uvc_queue_head(struct uvc_video_queue *queue)
 {
 	struct uvc_buffer *buf = NULL;

 	if (!list_empty(&queue->irqqueue))
 		buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
 				       queue);
 	else
 		queue->flags |= UVC_QUEUE_PAUSED;

 	return buf;
 }
	/*
	* uvc_queue.c -- USB Video Class driver - Buffers management
	*
	* Copyright (C) 2005-2010
	* Laurent Pinchart (laurent.pinchart@ideasonboard.com)
	*
	* 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.
	*/

	#include <linux/atomic.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/list.h>
	#include <linux/module.h>
	#include <linux/usb.h>
	#include <linux/videodev2.h>
	#include <linux/vmalloc.h>
	#include <linux/wait.h>

	#include <media/videobuf2-vmalloc.h>

	#include "uvc.h"

	/* ------------------------------------------------------------------------
	* Video buffers queue management.
	*
	* Video queues is initialized by uvc_queue_init(). The function performs
	* basic initialization of the uvc_video_queue struct and never fails.
	*
	* Video buffers are managed by videobuf2. The driver uses a mutex to protect
	* the videobuf2 queue operations by serializing calls to videobuf2 and a
	* spinlock to protect the IRQ queue that holds the buffers to be processed by
	* the driver.
	*/

	/* -----------------------------------------------------------------------------
	* videobuf2 queue operations
	*/

	static int uvc_queue_setup(struct vb2_queue vq, const struct v4l2_format fmt,
	unsigned int nbuffers, unsigned int nplanes,
	unsigned int sizes[], void *alloc_ctxs[])
	{
	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
	struct uvc_video *video = container_of(queue, struct uvc_video, queue);

	if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
	*nbuffers = UVC_MAX_VIDEO_BUFFERS;

	*nplanes = 1;

	sizes[0] = video->imagesize;

	return 0;
	}

	static int uvc_buffer_prepare(struct vb2_buffer *vb)
	{
	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
	struct uvc_buffer *buf = container_of(vb, struct uvc_buffer, buf);

	if (vb->v4l2_buf.type == V4L2_BUF_TYPE_VIDEO_OUTPUT &&
	vb2_get_plane_payload(vb, 0) > vb2_plane_size(vb, 0)) {
	uvc_trace(UVC_TRACE_CAPTURE, "[E] Bytes used out of bounds.\n");
	return -EINVAL;
	}

	if (unlikely(queue->flags & UVC_QUEUE_DISCONNECTED))
	return -ENODEV;

	buf->state = UVC_BUF_STATE_QUEUED;
	buf->mem = vb2_plane_vaddr(vb, 0);
	buf->length = vb2_plane_size(vb, 0);
	if (vb->v4l2_buf.type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
	buf->bytesused = 0;
	else
	buf->bytesused = vb2_get_plane_payload(vb, 0);

	return 0;
	}

	static void uvc_buffer_queue(struct vb2_buffer *vb)
	{
	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
	struct uvc_buffer *buf = container_of(vb, struct uvc_buffer, buf);
	unsigned long flags;

	spin_lock_irqsave(&queue->irqlock, flags);

	if (likely(!(queue->flags & UVC_QUEUE_DISCONNECTED))) {
	list_add_tail(&buf->queue, &queue->irqqueue);
	} else {
	/* If the device is disconnected return the buffer to userspace
	* directly. The next QBUF call will fail with -ENODEV.
	*/
	buf->state = UVC_BUF_STATE_ERROR;
	vb2_buffer_done(&buf->buf, VB2_BUF_STATE_ERROR);
	}

	spin_unlock_irqrestore(&queue->irqlock, flags);
	}

	static struct vb2_ops uvc_queue_qops = {
	.queue_setup = uvc_queue_setup,
	.buf_prepare = uvc_buffer_prepare,
	.buf_queue = uvc_buffer_queue,
	};

	static int uvc_queue_init(struct uvc_video_queue *queue,
	enum v4l2_buf_type type)
	{
	int ret;

	queue->queue.type = type;
	queue->queue.io_modes = VB2_MMAP \| VB2_USERPTR;
	queue->queue.drv_priv = queue;
	queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
	queue->queue.ops = &uvc_queue_qops;
	queue->queue.mem_ops = &vb2_vmalloc_memops;
	ret = vb2_queue_init(&queue->queue);
	if (ret)
	return ret;

	mutex_init(&queue->mutex);
	spin_lock_init(&queue->irqlock);
	INIT_LIST_HEAD(&queue->irqqueue);
	queue->flags = 0;

	return 0;
	}

	/*
	* Free the video buffers.
	*/
	static void uvc_free_buffers(struct uvc_video_queue *queue)
	{
	mutex_lock(&queue->mutex);
	vb2_queue_release(&queue->queue);
	mutex_unlock(&queue->mutex);
	}

	/*
	* Allocate the video buffers.
	*/
	static int uvc_alloc_buffers(struct uvc_video_queue *queue,
	struct v4l2_requestbuffers *rb)
	{
	int ret;

	mutex_lock(&queue->mutex);
	ret = vb2_reqbufs(&queue->queue, rb);
	mutex_unlock(&queue->mutex);

	return ret ? ret : rb->count;
	}

	static int uvc_query_buffer(struct uvc_video_queue *queue,
	struct v4l2_buffer *buf)
	{
	int ret;

	mutex_lock(&queue->mutex);
	ret = vb2_querybuf(&queue->queue, buf);
	mutex_unlock(&queue->mutex);

	return ret;
	}

	static int uvc_queue_buffer(struct uvc_video_queue *queue,
	struct v4l2_buffer *buf)
	{
	unsigned long flags;
	int ret;

	mutex_lock(&queue->mutex);
	ret = vb2_qbuf(&queue->queue, buf);
	spin_lock_irqsave(&queue->irqlock, flags);
	ret = (queue->flags & UVC_QUEUE_PAUSED) != 0;
	queue->flags &= ~UVC_QUEUE_PAUSED;
	spin_unlock_irqrestore(&queue->irqlock, flags);
	mutex_unlock(&queue->mutex);

	return ret;
	}

	/*
	* Dequeue a video buffer. If nonblocking is false, block until a buffer is
	* available.
	*/
	static int uvc_dequeue_buffer(struct uvc_video_queue *queue,
	struct v4l2_buffer *buf, int nonblocking)
	{
	int ret;

	mutex_lock(&queue->mutex);
	ret = vb2_dqbuf(&queue->queue, buf, nonblocking);
	mutex_unlock(&queue->mutex);

	return ret;
	}

	/*
	* Poll the video queue.
	*
	* This function implements video queue polling and is intended to be used by
	* the device poll handler.
	*/
	static unsigned int uvc_queue_poll(struct uvc_video_queue *queue,
	struct file file, poll_table wait)
	{
	unsigned int ret;

	mutex_lock(&queue->mutex);
	ret = vb2_poll(&queue->queue, file, wait);
	mutex_unlock(&queue->mutex);

	return ret;
	}

	static int uvc_queue_mmap(struct uvc_video_queue *queue,
	struct vm_area_struct *vma)
	{
	int ret;

	mutex_lock(&queue->mutex);
	ret = vb2_mmap(&queue->queue, vma);
	mutex_unlock(&queue->mutex);

	return ret;
	}

	#ifndef CONFIG_MMU
	/*
	* Get unmapped area.
	*
	* NO-MMU arch need this function to make mmap() work correctly.
	*/
	static unsigned long uvc_queue_get_unmapped_area(struct uvc_video_queue *queue,
	unsigned long pgoff)
	{
	unsigned long ret;

	mutex_lock(&queue->mutex);
	ret = vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
	mutex_unlock(&queue->mutex);
	return ret;
	}
	#endif

	/*
	* Cancel the video buffers queue.
	*
	* Cancelling the queue marks all buffers on the irq queue as erroneous,
	* wakes them up and removes them from the queue.
	*
	* If the disconnect parameter is set, further calls to uvc_queue_buffer will
	* fail with -ENODEV.
	*
	* This function acquires the irq spinlock and can be called from interrupt
	* context.
	*/
	static void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect)
	{
	struct uvc_buffer *buf;
	unsigned long flags;

	spin_lock_irqsave(&queue->irqlock, flags);
	while (!list_empty(&queue->irqqueue)) {
	buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
	queue);
	list_del(&buf->queue);
	buf->state = UVC_BUF_STATE_ERROR;
	vb2_buffer_done(&buf->buf, VB2_BUF_STATE_ERROR);
	}
	/* This must be protected by the irqlock spinlock to avoid race
	* conditions between uvc_queue_buffer and the disconnection event that
	* could result in an interruptible wait in uvc_dequeue_buffer. Do not
	* blindly replace this logic by checking for the UVC_DEV_DISCONNECTED
	* state outside the queue code.
	*/
	if (disconnect)
	queue->flags \|= UVC_QUEUE_DISCONNECTED;
	spin_unlock_irqrestore(&queue->irqlock, flags);
	}

	/*
	* Enable or disable the video buffers queue.
	*
	* The queue must be enabled before starting video acquisition and must be
	* disabled after stopping it. This ensures that the video buffers queue
	* state can be properly initialized before buffers are accessed from the
	* interrupt handler.
	*
	* Enabling the video queue initializes parameters (such as sequence number,
	* sync pattern, ...). If the queue is already enabled, return -EBUSY.
	*
	* Disabling the video queue cancels the queue and removes all buffers from
	* the main queue.
	*
	* This function can't be called from interrupt context. Use
	* uvc_queue_cancel() instead.
	*/
	static int uvc_queue_enable(struct uvc_video_queue *queue, int enable)
	{
	unsigned long flags;
	int ret = 0;

	mutex_lock(&queue->mutex);
	if (enable) {
	ret = vb2_streamon(&queue->queue, queue->queue.type);
	if (ret < 0)
	goto done;

	queue->sequence = 0;
	queue->buf_used = 0;
	} else {
	ret = vb2_streamoff(&queue->queue, queue->queue.type);
	if (ret < 0)
	goto done;

	spin_lock_irqsave(&queue->irqlock, flags);
	INIT_LIST_HEAD(&queue->irqqueue);

	/*
	* FIXME: We need to clear the DISCONNECTED flag to ensure that
	* applications will be able to queue buffers for the next
	* streaming run. However, clearing it here doesn't guarantee
	* that the device will be reconnected in the meantime.
	*/
	queue->flags &= ~UVC_QUEUE_DISCONNECTED;
	spin_unlock_irqrestore(&queue->irqlock, flags);
	}

	done:
	mutex_unlock(&queue->mutex);
	return ret;
	}

	/* called with &queue_irqlock held.. */
	static struct uvc_buffer uvc_queue_next_buffer(struct uvc_video_queue queue,
	struct uvc_buffer *buf)
	{
	struct uvc_buffer *nextbuf;

	if ((queue->flags & UVC_QUEUE_DROP_INCOMPLETE) &&
	buf->length != buf->bytesused) {
	buf->state = UVC_BUF_STATE_QUEUED;
	vb2_set_plane_payload(&buf->buf, 0, 0);
	return buf;
	}

	list_del(&buf->queue);
	if (!list_empty(&queue->irqqueue))
	nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
	queue);
	else
	nextbuf = NULL;

	/*
	* FIXME: with videobuf2, the sequence number or timestamp fields
	* are valid only for video capture devices and the UVC gadget usually
	* is a video output device. Keeping these until the specs are clear on
	* this aspect.
	*/
	buf->buf.v4l2_buf.sequence = queue->sequence++;
	do_gettimeofday(&buf->buf.v4l2_buf.timestamp);

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

	return nextbuf;
	}

	static struct uvc_buffer uvc_queue_head(struct uvc_video_queue queue)
	{
	struct uvc_buffer *buf = NULL;

	if (!list_empty(&queue->irqqueue))
	buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
	queue);
	else
	queue->flags \|= UVC_QUEUE_PAUSED;

	return buf;
	}