Re: [PATCH RFC v2] media: v4l2-ctrl: Add gain controls

From: Hans Verkuil
Date: Wed Dec 05 2012 - 07:18:35 EST


(resend without HTML formatting)

On Wed 5 December 2012 12:49:29 Prabhakar Lad wrote:
> From: Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx>
>
> add support for per color component digital/analog gain controls
> and also their corresponding offset.

Some obvious questions below...

>
> Signed-off-by: Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx>
> Cc: Sakari Ailus <sakari.ailus@xxxxxx>
> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Cc: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> Cc: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
> Cc: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
> Cc: Chris MacGregor <chris@xxxxxxxxxxxxx>
> Cc: Rob Landley <rob@xxxxxxxxxxx>
> Cc: Jeongtae Park <jtp.park@xxxxxxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
> ---
> Changes for v2:
> 1: Fixed review comments pointed by Laurent.
> 2: Rebased on latest tree.
>
> Documentation/DocBook/media/v4l/controls.xml | 54 ++++++++++++++++++++++++++
> drivers/media/v4l2-core/v4l2-ctrls.c | 11 +++++
> include/uapi/linux/v4l2-controls.h | 11 +++++
> 3 files changed, 76 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
> index 7fe5be1..847a9bb 100644
> --- a/Documentation/DocBook/media/v4l/controls.xml
> +++ b/Documentation/DocBook/media/v4l/controls.xml
> @@ -4543,6 +4543,60 @@ interface and may change in the future.</para>
> specific test patterns can be used to test if a device is working
> properly.</entry>
> </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GAIN_RED</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GAIN_GREEN_RED</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GAIN_GREEN_BLUE</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GAIN_BLUE</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GAIN_GREEN</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="descr"> Some capture/sensor devices have
> + the capability to set per color component digital/analog gain values.</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GAIN_OFFSET</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_BLUE_OFFSET</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_RED_OFFSET</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GREEN_OFFSET</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GREEN_RED_OFFSET</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="id"><constant>V4L2_CID_GREEN_BLUE_OFFSET</constant></entry>
> + <entry>integer</entry>
> + </row>
> + <row>
> + <entry spanname="descr"> Some capture/sensor devices have the
> + capability to set per color component digital/analog gain offset values.
> + V4L2_CID_GAIN_OFFSET is the global gain offset and the rest are per
> + color component gain offsets.</entry>

If I set both V4L2_CID_GAIN_RED and V4L2_CID_RED_OFFSET, how are they supposed
to interact? Or are they mutually exclusive?

And if I set both V4L2_CID_GAIN_OFFSET and V4L2_CID_RED_OFFSET, how are they supposed
to interact?

This questions should be answered in the documentation...

Regards,

Hans

> + </row>
> <row><entry></entry></row>
> </tbody>
> </tgroup>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index f6ee201..05e3708 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -790,6 +790,17 @@ const char *v4l2_ctrl_get_name(u32 id)
> case V4L2_CID_LINK_FREQ: return "Link Frequency";
> case V4L2_CID_PIXEL_RATE: return "Pixel Rate";
> case V4L2_CID_TEST_PATTERN: return "Test Pattern";
> + case V4L2_CID_GAIN_RED: return "Gain Red";
> + case V4L2_CID_GAIN_GREEN_RED: return "Gain Green Red";
> + case V4L2_CID_GAIN_GREEN_BLUE: return "Gain Green Blue";
> + case V4L2_CID_GAIN_BLUE: return "Gain Blue";
> + case V4L2_CID_GAIN_GREEN: return "Gain Green";
> + case V4L2_CID_GAIN_OFFSET: return "Gain Offset";
> + case V4L2_CID_BLUE_OFFSET: return "Gain Blue Offset";
> + case V4L2_CID_RED_OFFSET: return "Gain Red Offset";
> + case V4L2_CID_GREEN_OFFSET: return "Gain Green Offset";
> + case V4L2_CID_GREEN_RED_OFFSET: return "Gain Green Red Offset";
> + case V4L2_CID_GREEN_BLUE_OFFSET: return "Gain Green Blue Offset";
>
> /* DV controls */
> case V4L2_CID_DV_CLASS: return "Digital Video Controls";
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index f56c945..9b6b233 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -799,5 +799,16 @@ enum v4l2_jpeg_chroma_subsampling {
> #define V4L2_CID_LINK_FREQ (V4L2_CID_IMAGE_PROC_CLASS_BASE + 1)
> #define V4L2_CID_PIXEL_RATE (V4L2_CID_IMAGE_PROC_CLASS_BASE + 2)
> #define V4L2_CID_TEST_PATTERN (V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
> +#define V4L2_CID_GAIN_RED (V4L2_CID_IMAGE_PROC_CLASS_BASE + 4)
> +#define V4L2_CID_GAIN_GREEN_RED (V4L2_CID_IMAGE_PROC_CLASS_BASE + 5)
> +#define V4L2_CID_GAIN_GREEN_BLUE (V4L2_CID_IMAGE_PROC_CLASS_BASE + 6)
> +#define V4L2_CID_GAIN_BLUE (V4L2_CID_IMAGE_PROC_CLASS_BASE + 7)
> +#define V4L2_CID_GAIN_GREEN (V4L2_CID_IMAGE_PROC_CLASS_BASE + 8)
> +#define V4L2_CID_GAIN_OFFSET (V4L2_CID_IMAGE_PROC_CLASS_BASE + 9)
> +#define V4L2_CID_BLUE_OFFSET (V4L2_CID_IMAGE_PROC_CLASS_BASE + 10)
> +#define V4L2_CID_RED_OFFSET (V4L2_CID_IMAGE_PROC_CLASS_BASE + 11)
> +#define V4L2_CID_GREEN_OFFSET (V4L2_CID_IMAGE_PROC_CLASS_BASE + 12)
> +#define V4L2_CID_GREEN_RED_OFFSET (V4L2_CID_IMAGE_PROC_CLASS_BASE + 13)
> +#define V4L2_CID_GREEN_BLUE_OFFSET (V4L2_CID_IMAGE_PROC_CLASS_BASE + 14)
>
> #endif
>
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