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

[Hans Verkuil <hverkuil@xs4all.nl>]

(resend without HTML formatting)

On Wed 5 December 2012 12:49:29 Prabhakar Lad wrote:
> From: Lad, Prabhakar <prabhakar.csengg@gmail.com>
> 
> 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@gmail.com>
> Cc: Sakari Ailus <sakari.ailus@iki.fi>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
> Cc: Hans Verkuil <hans.verkuil@cisco.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Chris MacGregor <chris@cybermato.com>
> Cc: Rob Landley <rob@landley.net>
> Cc: Jeongtae Park <jtp.park@samsung.com>
> Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
> ---
>  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
>