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: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
---
Changes since v4:
- Split out DocBook changes into a separate patch.
- Documented last_buffer_dequeued flag in vb2_queue comment.
- Moved last_buffer_dequeued check from vb2_internal_dqbuf
into __vb2_wait_for_done_vb.
- Dropped superfluous check in vb2_poll.
---
drivers/media/v4l2-core/v4l2-mem2mem.c | 10 +++++++++-
drivers/media/v4l2-core/videobuf2-core.c | 19 ++++++++++++++++++-
include/media/videobuf2-core.h | 13 +++++++++++++
3 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 80c588f..1b5b432 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -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)
m2m_ctx->m2m_dev->m2m_ops->lock(m2m_ctx->priv);
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index cc16e76..3b2188e 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1918,6 +1918,11 @@ 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.
@@ -2073,6 +2078,9 @@ static int vb2_internal_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool n
/* Remove from videobuf queue */
list_del(&vb->queued_entry);
q->queued_count--;
+ 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 */
__vb2_dqbuf(vb);
@@ -2286,6 +2294,7 @@ static int vb2_internal_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
*/
__vb2_queue_cancel(q);
q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
+ q->last_buffer_dequeued = false;
dprintk(3, "successful\n");
return 0;
@@ -2628,8 +2637,16 @@ 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.
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index bd2cec2..a689d25 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -390,6 +390,9 @@ 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
*/
@@ -429,6 +432,7 @@ 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;
@@ -609,6 +613,15 @@ 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,
--
2.1.4
--
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