[PATCH v5 5/6] media: meson: vdec: Isolate error path buffer flush to the active queue

[Anand Moon <linux.amoon@gmail.com>]

When vdec_start_streaming() fails, the error path clears buffers from both
the source and destination queues unconditionally. If one queue was already
streaming successfully from a prior invocation, flushing its buffers behind
its back leaves videobuf2 deadlocked waiting for completions.

Fix this by only sweeping buffers from the specific queue type container
that failed to initialize.

Cc: Nicolas Dufresne <nicolas@ndufresne.ca>
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260521090944.F35401F00A3D@smtp.kernel.org/
Fixes: 3e7f51bd9607 ("media: meson: add v4l2 m2m video decoder driver")
Signed-off-by: Anand Moon <linux.amoon@gmail.com>
---
v5:
This is a pre-existing issue, but will returning buffers for both queues upon
a single-queue failure orphan active queue buffers?

If the CAPTURE queue was successfully started in a previous call, returning
its buffers puts them back into the vb2 queued list while the driver
discards its references. Because the CAPTURE queue remains active,
userspace calling DQBUF will hang indefinitely waiting for frames that
the driver will never process.
---
 drivers/staging/media/meson/vdec/vdec.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c
index b31bf08af88e..925537bd4d0b 100644
--- a/drivers/staging/media/meson/vdec/vdec.c
+++ b/drivers/staging/media/meson/vdec/vdec.c
@@ -372,15 +372,15 @@ static int vdec_start_streaming(struct vb2_queue *q, unsigned int count)
 	dma_free_coherent(sess->core->dev, sess->vififo_size,
 			  sess->vififo_vaddr, sess->vififo_paddr);
 bufs_done:
-	while ((buf = v4l2_m2m_src_buf_remove(sess->m2m_ctx)))
-		v4l2_m2m_buf_done(buf, VB2_BUF_STATE_QUEUED);
-	while ((buf = v4l2_m2m_dst_buf_remove(sess->m2m_ctx)))
-		v4l2_m2m_buf_done(buf, VB2_BUF_STATE_QUEUED);
-
-	if (q->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE)
+	if (q->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE) {
 		sess->streamon_out = 0;
-	else
+		while ((buf = v4l2_m2m_src_buf_remove(sess->m2m_ctx)))
+			v4l2_m2m_buf_done(buf, VB2_BUF_STATE_QUEUED);
+	} else {
 		sess->streamon_cap = 0;
+		while ((buf = v4l2_m2m_dst_buf_remove(sess->m2m_ctx)))
+			v4l2_m2m_buf_done(buf, VB2_BUF_STATE_QUEUED);
+	}
 
 	return ret;
 }
-- 
2.50.1