linux-kernel - Re: Support for RGB/YUV 10, 12 BPC(bits per color/component) image data formats in kernel

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Date:   Tue, 6 Jun 2017 12:05:44 +0530
From:   Ajay kumar <ajaynumb@...il.com>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-media <linux-media@...r.kernel.org>
Subject: Re: Support for RGB/YUV 10, 12 BPC(bits per color/component) image
 data formats in kernel

Hi Sakari,

On Sat, Jun 3, 2017 at 1:48 PM, Sakari Ailus <sakari.ailus@....fi> wrote:
> Hi Ajay,
>
> On Fri, Jun 02, 2017 at 06:38:53PM +0530, Ajay kumar wrote:
>> Hi all,
>>
>> I have tried searching for RGB/YUV 10, 12 BPC formats in videodev2.h,
>> media-bus-format.h and drm_fourcc.h
>> I could only find RGB 10BPC support in drm_fourcc.h.
>> I guess not much support is present for formats with (BPC > 8) in the kernel.
>
> What's "BPC"? Most YUV and RGB formats have only 8 bits per sample. More
> format definitions may be added if there's a driver that makes use of them.
BPC : Bits Per Color/Component
In my project, we have an image capture device which can capture 10 or
12 bits for each of R, G, B colors, i.e:
R[0:9] G[0:9] B[0:9] and
R[0:11] G[0:11] B[0:11]

I want to define macros for the above formats in videodev2.h.
But, I am not getting the logic behind the naming convention used to
define v4l2_fourcc macros.
ex:
V4L2_PIX_FMT_ARGB32      v4l2_fourcc('A', 'R', '2', '4');

How did they choose the characters 'A', 'R', '2', '4' in the above case?

I want to know the logic/naming convention behind that, so that I can create
new v4l2_fourcc defines for 10, 12 BPC formats and use in my driver.

Thanks,
Ajay Kumar
>>
>> Are there any plans to add fourcc defines for such formats?
>> Also, I wanted to how to define fourcc code for those formats?
>
> --
> Regards,
>
> Sakari Ailus
> e-mail: sakari.ailus@....fi     XMPP: sailus@...iisi.org.uk