[PATCH v2 08/17] media: v4l2-subdev: Always return at least one frame descriptor

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Make v4l2_subdev_get_frame_desc() return at least one frame descriptor
entry or an error. Empty frame descriptors aren't useful for callers so
callers can now omit this check.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 6 ++++++
 include/media/v4l2-subdev.h           | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index b5eef0baa237..dc4ac08c210f 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -2732,6 +2732,12 @@ v4l2_subdev_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
 			goto err_free;
 		}
 
+		if (!desc->num_entries) {
+			dev_dbg(sd->dev, "no frame descriptor entries\n");
+			ret = -EINVAL;
+			goto err_free;
+		}
+
 		return desc;
 	}
 
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index f9b121eefa92..0361c8bbee38 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -1817,6 +1817,8 @@ int v4l2_subdev_get_frame_desc_passthrough(struct v4l2_subdev *sd,
  *    struct v4l2_mbus_frame_desc *desc __free(v4l2_subdev_free_frame_desc) =
  *            v4l2_subdev_get_frame_desc(sd, pad, desc);
  *
+ * The returned frame descriptor will contain at least one entry.
+ *
  * Return: The frame descriptor on success or a negative error code on failure.
  */
 struct v4l2_mbus_frame_desc *
-- 
2.47.3