media: v4l2-subdev: Add which field to struct v4l2_subdev_frame_interval

Due to a historical mishap, the v4l2_subdev_frame_interval structure
is the only part of the V4L2 subdev userspace API that doesn't contain a
'which' field. This prevents trying frame intervals using the subdev
'TRY' state mechanism.

Adding a 'which' field is simple as the structure has 8 reserved fields.
This would however break userspace as the field is currently set to 0,
corresponding to V4L2_SUBDEV_FORMAT_TRY, while the corresponding ioctls
currently operate on the 'ACTIVE' state. We thus need to add a new
subdev client cap, V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH, to
indicate that userspace is aware of this new field.

All drivers that implement the subdev .get_frame_interval() and
.set_frame_interval() operations are updated to return -EINVAL when
operating on the TRY state, preserving the current behaviour.

While at it, fix a bad copy&paste in the documentation of the struct
v4l2_subdev_frame_interval_enum 'which' field.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de> # for imx-media
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com> # for tegra-video
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

1 files changed, 12 insertions, 3 deletions

diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
index f0fbb4a7c150..7048c51581c6 100644
--- a/include/uapi/linux/v4l2-subdev.h
+++ b/include/uapi/linux/v4l2-subdev.h
@@ -116,13 +116,15 @@ struct v4l2_subdev_frame_size_enum {
  * @pad: pad number, as reported by the media API
  * @interval: frame interval in seconds
  * @stream: stream number, defined in subdev routing
+ * @which: interval type (from enum v4l2_subdev_format_whence)
  * @reserved: drivers and applications must zero this array
  */
 struct v4l2_subdev_frame_interval {
 	__u32 pad;
 	struct v4l2_fract interval;
 	__u32 stream;
-	__u32 reserved[8];
+	__u32 which;
+	__u32 reserved[7];
 };
 
 /**
@@ -133,7 +135,7 @@ struct v4l2_subdev_frame_interval {
  * @width: frame width in pixels
  * @height: frame height in pixels
  * @interval: frame interval in seconds
- * @which: format type (from enum v4l2_subdev_format_whence)
+ * @which: interval type (from enum v4l2_subdev_format_whence)
  * @stream: stream number, defined in subdev routing
  * @reserved: drivers and applications must zero this array
  */
@@ -239,7 +241,14 @@ struct v4l2_subdev_routing {
  * set (which is the default), the 'stream' fields will be forced to 0 by the
  * kernel.
  */
-#define V4L2_SUBDEV_CLIENT_CAP_STREAMS		(1ULL << 0)
+#define V4L2_SUBDEV_CLIENT_CAP_STREAMS			(1ULL << 0)
+
+/*
+ * The client is aware of the struct v4l2_subdev_frame_interval which field. If
+ * this is not set (which is the default), the which field is forced to
+ * V4L2_SUBDEV_FORMAT_ACTIVE by the kernel.
+ */
+#define V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH	(1ULL << 1)
 
 /**
  * struct v4l2_subdev_client_capability - Capabilities of the client accessing