Re: [PATCH v3 2/2] media: v4l2-ctrls: Document V4L2_CID_NOTIFY_GAIN_XXX controls

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

On 22/07/2021 14:12, David Plowman wrote:
> Add documentation for each of the controls
> 
> V4L2_CID_NOTIFY_GAIN_RED
> V4L2_CID_NOTIFY_GAIN_GREENR
> V4L2_CID_NOTIFY_GAIN_BLUE
> V4L2_CID_NOTIFY_GAIN_GREENB
> 
> These controls are required by sensors that need to know what colour
> gains will be applied to pixels by downstream processing (such as by
> an ISP), though the sensor does not apply these gains itself.
> 
> Signed-off-by: David Plowman <david.plowman@raspberrypi.com>

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans

> ---
>  .../media/v4l/ext-ctrls-image-source.rst      | 25 +++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
> index de43f5c8486d..d50b56156a8e 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
> @@ -72,3 +72,28 @@ Image Source Control IDs
>      * - __u32
>        - ``height``
>        - Height of the area.
> +
> +``V4L2_CID_NOTIFY_GAIN_RED (integer)``
> +    Please refer to ``V4L2_CID_NOTIFY_GAIN_GREENB`` below.
> +
> +``V4L2_CID_NOTIFY_GAIN_GREENR (integer)``
> +    Please refer to ``V4L2_CID_NOTIFY_GAIN_GREENB`` below.
> +
> +``V4L2_CID_NOTIFY_GAIN_BLUE (integer)``
> +    Please refer to ``V4L2_CID_NOTIFY_GAIN_GREENB`` below.
> +
> +``V4L2_CID_NOTIFY_GAIN_GREENB (integer)``
> +    Note: this description covers all four ``V4L2_CID_NOTIFY_GAIN``
> +    controls, according to the Bayer channel indicated at the end of
> +    the control name.
> +
> +    The sensor is notified what gain will be applied to this Bayer
> +    channel by subsequent processing (such as by an ISP). The sensor
> +    is merely informed of this value in case it performs processing
> +    that requires it, but it does not apply it to the output pixels
> +    themselves.
> +
> +    The units for the gain value are linear, with the default value
> +    being shared between all four controls and representing a gain of
> +    exactly 1. Other control properties, such as ranges, should also
> +    be common.
>