From d4de27a9b1eadd33a2e40de87a646d1bf5fef756 Mon Sep 17 00:00:00 2001
From: Ming Qian <ming.qian@nxp.com>
Date: Wed, 15 Jun 2022 04:19:20 +0100
Subject: [PATCH] media: v4l2-mem2mem: prevent pollerr when last_buffer_dequeued is set
Git-commit: d4de27a9b1eadd33a2e40de87a646d1bf5fef756
Patch-mainline: v6.0-rc1
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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);
-- 
2.35.3