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    Subject[PATCH 5.18 0376/1095] media: v4l2-mem2mem: prevent pollerr when last_buffer_dequeued is set
    Date
    From: Ming Qian <ming.qian@nxp.com>

    [ Upstream commit d4de27a9b1eadd33a2e40de87a646d1bf5fef756 ]

    If the last buffer was dequeued from the capture queue,
    signal userspace. DQBUF(CAPTURE) will return -EPIPE.

    But if output queue is empty and capture queue is empty,
    v4l2_m2m_poll_for_data will return EPOLLERR,
    This is very easy to happen in drain.

    When last_buffer_dequeued is set, we shouldn't return EPOLLERR,
    but return EPOLLIN | EPOLLRDNORM.

    Fixes: 1698a7f151126 ("media: v4l2-mem2mem: simplify poll logic")
    Signed-off-by: Ming Qian <ming.qian@nxp.com>
    Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
    Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/media/v4l2-core/v4l2-mem2mem.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
    index 675e22895ebe..094e1815209b 100644
    --- a/drivers/media/v4l2-core/v4l2-mem2mem.c
    +++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
    @@ -924,7 +924,7 @@ static __poll_t v4l2_m2m_poll_for_data(struct file *file,
    if ((!src_q->streaming || src_q->error ||
    list_empty(&src_q->queued_list)) &&
    (!dst_q->streaming || dst_q->error ||
    - list_empty(&dst_q->queued_list)))
    + (list_empty(&dst_q->queued_list) && !dst_q->last_buffer_dequeued)))
    return EPOLLERR;

    spin_lock_irqsave(&src_q->done_lock, flags);
    --
    2.35.1


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