On 09/08/2021 11:34, David Plowman wrote:
> We add a new control V4L2_CID_NOTIFY_GAINS which allows the sensor to
> be notified what gains will be applied to the different colour
> channels by subsequent processing (such as by an ISP), even though the
> sensor will not apply any of these gains itself.
>
> For Bayer sensors this will be an array control taking 4 values which
> are the 4 gains arranged in the fixed order B, Gb, Gr and R,
> irrespective of the exact Bayer order of the sensor itself.
>
> The units are in all cases linear with the default value indicating a
> gain of exactly 1.
So a value of 2 means a gain of 2? Or are these fixed point values? How do
I represent a gain of 1.5?
>
> Signed-off-by: David Plowman <david.plowman@xxxxxxxxxxxxxxx>
> ---
> drivers/media/v4l2-core/v4l2-ctrls-defs.c | 1 +
> include/uapi/linux/v4l2-controls.h | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> index 421300e13a41..f87053c83249 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -1107,6 +1107,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> case V4L2_CID_TEST_PATTERN_GREENR: return "Green (Red) Pixel Value";
> case V4L2_CID_TEST_PATTERN_BLUE: return "Blue Pixel Value";
> case V4L2_CID_TEST_PATTERN_GREENB: return "Green (Blue) Pixel Value";
> + case V4L2_CID_NOTIFY_GAINS: return "Notify Gains";
>
> /* Image processing controls */
> /* Keep the order of the 'case's the same as in v4l2-controls.h! */
Since this is a standard control, it should also be configured correctly in
v4l2_ctrl_fill().
Instead of an array, would a compound control (aka a struct) be better? Then you can
explicitly have field names g, gb, gr and r.
Is there a specific reason we want an array instead of that? I'm not opposed, but
I'd like to see a rationale for that.
Regards,
Hans
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 5532b5f68493..133e20444939 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -1118,6 +1118,7 @@ enum v4l2_jpeg_chroma_subsampling {
> #define V4L2_CID_TEST_PATTERN_BLUE (V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 6)
> #define V4L2_CID_TEST_PATTERN_GREENB (V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 7)
> #define V4L2_CID_UNIT_CELL_SIZE (V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 8)
> +#define V4L2_CID_NOTIFY_GAINS (V4L2_CID_IMAGE_SOURCE_CLASS_BASE + 9)
>
>
> /* Image processing controls */
>
