[PATCH v2] v4l2-subdev: Return -EOPNOTSUPP for unsupported pad type in call_get_frame_desc()

[Prabhakar]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

The `get_frame_desc()` operation should always be called on a source pad,
which is indicated by the `MEDIA_PAD_FL_SOURCE` flag. This patch adds a
check in `call_get_frame_desc()` to ensure that the `MEDIA_PAD_FL_SOURCE`
flag is set for the pad before invoking `get_frame_desc()`. If the pad is
not a source pad, the function will return an `-EOPNOTSUPP` error,
signaling that the operation is not supported on non-source pads.

Suggested-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
---
v1->v2
- Added a check for CONFIG_MEDIA_CONTROLLER, as the `entity` member in 
  `struct v4l2_subdev` is only available when CONFIG_MEDIA_CONTROLLER
  is enabled.
---
 drivers/media/v4l2-core/v4l2-subdev.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index de9ac67574bb..446fbc3805c7 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -325,6 +325,11 @@ static int call_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
 	unsigned int i;
 	int ret;
 
+#if defined(CONFIG_MEDIA_CONTROLLER)
+	if (!(sd->entity.pads[pad].flags & MEDIA_PAD_FL_SOURCE))
+		return -EOPNOTSUPP;
+#endif
+
 	memset(fd, 0, sizeof(*fd));
 
 	ret = sd->ops->pad->get_frame_desc(sd, pad, fd);
-- 
2.43.0