Explicitly document that the driver-specific buffer structure
must start with the subsystem-specific struct (vb2_v4l2_buffer
in the case of V4L2).
Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
---
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index a2b2208b02da..f11b96514cf7 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -509,8 +509,11 @@ struct vb2_buf_ops {
* by the vb2 core.
* @buf_struct_size: size of the driver-specific buffer structure;
* "0" indicates the driver doesn't want to use a custom buffer
- * structure type. for example, ``sizeof(struct vb2_v4l2_buffer)``
- * will be used for v4l2.
+ * structure type. In that case a subsystem-specific struct
+ * will be used (in the case of V4L2 that is
+ * ``sizeof(struct vb2_v4l2_buffer)``). The first field of the
+ * driver-specific buffer structure must be the subsystem-specific
+ * struct (vb2_v4l2_buffer in the case of V4L2).
* @timestamp_flags: Timestamp flags; ``V4L2_BUF_FLAG_TIMESTAMP_*`` and
* ``V4L2_BUF_FLAG_TSTAMP_SRC_*``
* @gfp_flags: additional gfp flags used when allocating the buffers.
