Commit c1621840 authored by Philipp Zabel's avatar Philipp Zabel Committed by Mauro Carvalho Chehab

[media] videobuf2: return -EPIPE from DQBUF after the last buffer

If the last buffer was dequeued from a capture queue, let poll return
immediately and let DQBUF return -EPIPE to signal there will no more
buffers to dequeue until STREAMOFF.
The driver signals the last buffer by setting the V4L2_BUF_FLAG_LAST.
To reenable dequeuing on the capture queue, the driver must explicitly
call vb2_clear_last_buffer_queued. The last buffer queued flag is
cleared automatically during STREAMOFF.
Signed-off-by: default avatarPhilipp Zabel <>
Acked-by: default avatarHans Verkuil <>
Signed-off-by: default avatarKamil Debski <>
Signed-off-by: default avatarMauro Carvalho Chehab <>
parent dc199241
......@@ -564,8 +564,16 @@ unsigned int v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
if (list_empty(&src_q->done_list))
poll_wait(file, &src_q->done_wq, wait);
if (list_empty(&dst_q->done_list))
if (list_empty(&dst_q->done_list)) {
* If the last buffer was dequeued from the capture queue,
* return immediately. DQBUF will return -EPIPE.
if (dst_q->last_buffer_dequeued)
return rc | POLLIN | POLLRDNORM;
poll_wait(file, &dst_q->done_wq, wait);
if (m2m_ctx->m2m_dev->m2m_ops->lock)
......@@ -1943,6 +1943,11 @@ static int __vb2_wait_for_done_vb(struct vb2_queue *q, int nonblocking)
return -EIO;
if (q->last_buffer_dequeued) {
dprintk(3, "last buffer dequeued already, will not wait for buffers\n");
return -EPIPE;
if (!list_empty(&q->done_list)) {
* Found a buffer that we were waiting for.
......@@ -2098,6 +2103,9 @@ static int vb2_internal_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool n
/* Remove from videobuf queue */
if (!V4L2_TYPE_IS_OUTPUT(q->type) &&
vb->v4l2_buf.flags & V4L2_BUF_FLAG_LAST)
q->last_buffer_dequeued = true;
/* go back to dequeued state */
......@@ -2311,6 +2319,7 @@ static int vb2_internal_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
q->last_buffer_dequeued = false;
dprintk(3, "successful\n");
return 0;
......@@ -2653,8 +2662,16 @@ unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait)
if (V4L2_TYPE_IS_OUTPUT(q->type) && q->queued_count < q->num_buffers)
return res | POLLOUT | POLLWRNORM;
if (list_empty(&q->done_list))
if (list_empty(&q->done_list)) {
* If the last buffer was dequeued from a capture queue,
* return immediately. DQBUF will return -EPIPE.
if (q->last_buffer_dequeued)
return res | POLLIN | POLLRDNORM;
poll_wait(file, &q->done_wq, wait);
* Take first buffer available for dequeuing.
......@@ -381,6 +381,9 @@ struct v4l2_fh;
* @waiting_for_buffers: used in poll() to check if vb2 is still waiting for
* buffers. Only set for capture queues if qbuf has not yet been
* called since poll() needs to return POLLERR in that situation.
* @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the
* last decoded buffer was already dequeued. Set for capture queues
* when a buffer with the V4L2_BUF_FLAG_LAST is dequeued.
* @fileio: file io emulator internal data, used only if emulator is active
* @threadio: thread io internal data, used only if thread is active
......@@ -423,6 +426,7 @@ struct vb2_queue {
unsigned int start_streaming_called:1;
unsigned int error:1;
unsigned int waiting_for_buffers:1;
unsigned int last_buffer_dequeued:1;
struct vb2_fileio_data *fileio;
struct vb2_threadio_data *threadio;
......@@ -603,6 +607,15 @@ static inline bool vb2_start_streaming_called(struct vb2_queue *q)
return q->start_streaming_called;
* vb2_clear_last_buffer_dequeued() - clear last buffer dequeued flag of queue
* @q: videobuf queue
static inline void vb2_clear_last_buffer_dequeued(struct vb2_queue *q)
q->last_buffer_dequeued = false;
* The following functions are not part of the vb2 core API, but are simple
* helper functions that you can use in your struct v4l2_file_operations,
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