[PATCH] media: v4l2-subdev: Clearly document that the crop API won't be extended

[Sakari Ailus]

Hi Laurent,

On Thu, Apr 04, 2024 at 05:56:49PM +0300, Laurent Pinchart wrote:
> The V4L2 subdev crop API has been marked as obsolete, deprecated by the
> selection API. Despite this, it has recently been extended with streams
> support. In hindsight this was a mistake. Make sure it doesn't happen
> again by clearly documenting that no new extensions will be accepted.
> 
> Suggested-by: Hans Verkuil <hverkuil-cisco at xs4all.nl>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  .../userspace-api/media/v4l/vidioc-subdev-g-crop.rst        | 6 +++---
>  include/uapi/linux/v4l2-subdev.h                            | 4 ++++
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> index 92d933631fda..88a748103a71 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
> @@ -37,9 +37,9 @@ Description
>  
>  .. note::
>  
> -    This is an :ref:`obsolete` interface and may be removed
> -    in the future. It is superseded by
> -    :ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`.
> +    This is an :ref:`obsolete` interface and may be removed in the future. It is
> +    superseded by :ref:`the selection API <VIDIOC_SUBDEV_G_SELECTION>`. No new
> +    extensions to the :c:type:`v4l2_subdev_crop` structure will be accepted.
>  
>  To retrieve the current crop rectangle applications set the ``pad``
>  field of a struct :c:type:`v4l2_subdev_crop` to the
> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> index 7048c51581c6..81a24bd38003 100644
> --- a/include/uapi/linux/v4l2-subdev.h
> +++ b/include/uapi/linux/v4l2-subdev.h
> @@ -50,6 +50,10 @@ struct v4l2_subdev_format {
>   * @rect: pad crop rectangle boundaries
>   * @stream: stream number, defined in subdev routing
>   * @reserved: drivers and applications must zero this array
> + *
> + * The subdev crop API is an obsolete interface and may be removed in the
> + * future. It is superseded by the selection API. No new extensions to this

I'm not sure we could ever remove this, however that doesn't mean the text
couldn't be added. :-) I'd still drop the latter part of the first
sentence. Up to you.

Acked-by: Sakari Ailus <sakari.ailus at linux.intel.com>

> + * structure will be accepted.
>   */
>  struct v4l2_subdev_crop {
>  	__u32 which;

-- 
Kind regards,

Sakari Ailus