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

From: Prabhakar Lad
Date: Wed Dec 05 2012 - 23:54:41 EST

Hi Hans,

On Wed, Dec 5, 2012 at 5:38 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> (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...
>
I haven’t worked on the hardware which supports both, What is the general
behaviour when the hardware supports both per color component and global
and both of them are set ? That could be helpful for me to document.

Regards,
--Prabhakar Lad

> 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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