linux-kernel - [PATCH v2 03/23] media: videobuf2-v4l2: Warn on holding buffers without support

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Date:   Thu, 31 Mar 2022 15:37:05 -0400
From:   Nicolas Dufresne <nicolas.dufresne@...labora.com>
To:     Tomasz Figa <tfiga@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     kernel@...labora.com,
        Sebastian Fricke <sebastian.fricke@...labora.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 03/23] media: videobuf2-v4l2: Warn on holding buffers without support

From: Sebastian Fricke <sebastian.fricke@...labora.com>

Using V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF flag without specifying the
subsystem flag VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF, results in
silently ignoring it.
Warn the user via a debug print when the flag is requested but ignored
by the videobuf2 framework.

Signed-off-by: Sebastian Fricke <sebastian.fricke@...labora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
---
 drivers/media/common/videobuf2/videobuf2-v4l2.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 6edf4508c636..812c8d1962e0 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -329,8 +329,13 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
 		 */
 		vbuf->flags &= ~V4L2_BUF_FLAG_TIMECODE;
 		vbuf->field = b->field;
-		if (!(q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF))
+		if (!(q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)) {
+			if (vbuf->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF)
+				dprintk(q, 1,
+					"Request holding buffer (%d), unsupported on output queue\n",
+					b->index);
 			vbuf->flags &= ~V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
+		}
 	} else {
 		/* Zero any output buffer flags as this is a capture buffer */
 		vbuf->flags &= ~V4L2_BUFFER_OUT_FLAGS;
-- 
2.34.1