linux-kernel - [PATCH] media: v4l2-mem2mem: prevent pollerr when last_buffer

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Message-Id: <20220615031920.16118-1-ming.qian@nxp.com>
Date:   Wed, 15 Jun 2022 11:19:20 +0800
From:   Ming Qian <ming.qian@....com>
To:     mchehab@...nel.org, hverkuil-cisco@...all.nl
Cc:     shawnguo@...nel.org, robh+dt@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] media: v4l2-mem2mem: prevent pollerr when last_buffer_dequeued is set

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@....com>
---
 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 6469f9a25a4e..837e1855f94b 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -925,7 +925,7 @@ 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);
-- 
2.36.1