[EXT] Re: [PATCH v2 02/10] media: Add Y012 video format

[Ming Qian]

>From: Nicolas Dufresne <nicolas at ndufresne.ca>
>Sent: 2023年2月10日 23:18
>To: Ming Qian <ming.qian at nxp.com>; mchehab at kernel.org; Mirela Rabulea
>(OSS) <mirela.rabulea at oss.nxp.com>; hverkuil-cisco at xs4all.nl
>Cc: shawnguo at kernel.org; s.hauer at pengutronix.de; kernel at pengutronix.de;
>festevam at gmail.com; X.H. Bao <xiahong.bao at nxp.com>; dl-linux-imx <linux-
>imx at nxp.com>; linux-media at vger.kernel.org; linux-kernel at vger.kernel.org;
>devicetree at vger.kernel.org; linux-arm-kernel at lists.infradead.org
>Subject: [EXT] Re: [PATCH v2 02/10] media: Add Y012 video format
>
>Caution: EXT Email
>
>Le mercredi 01 février 2023 à 14:02 +0800, Ming Qian a écrit :
>> Y012 is a luma-only formats with 12-bits per pixel, expanded to
>> 16bits.
>> Data in the 12 high bits, zeros in the 4 low bits, arranged in little
>> endian order.
>>
>> Signed-off-by: Ming Qian <ming.qian at nxp.com>
>> ---
>>  .../userspace-api/media/v4l/pixfmt-yuv-luma.rst       | 11 +++++++++++
>>  drivers/media/v4l2-core/v4l2-ioctl.c                  |  1 +
>>  include/uapi/linux/videodev2.h                        |  1 +
>>  3 files changed, 13 insertions(+)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
>> b/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
>> index 6a387f9df3ba..3ffa29000238 100644
>> --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
>> +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
>> @@ -103,6 +103,17 @@ are often referred to as greyscale formats.
>>        - ...
>>        - ...
>>
>> +    * .. _V4L2-PIX-FMT-Y012:
>
>Why the 0, can't this be name Y12 (just like Y14) ?
>

Hi Nicolas,
    As the V4L2_PIX_FMT_Y12 is defined, but it's data is in the 12 low bits, zeros in the high bits.
    Here I want to place the 12 bits data in the high bits, with zeros in the 4 low bits.
    So I add 0 before 12, I want to say that the low bits are padding data 0.
   
    Or do you have a better suggestion?

Ming

>> +
>> +      - ``V4L2_PIX_FMT_Y012``
>> +      - 'Y012'
>> +
>> +      - Y'\ :sub:`0`\ [3:0] `0000`
>> +      - Y'\ :sub:`0`\ [11:4]
>> +      - ...
>> +      - ...
>> +      - ...
>> +
>>      * .. _V4L2-PIX-FMT-Y14:
>>
>>        - ``V4L2_PIX_FMT_Y14``
>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c
>> b/drivers/media/v4l2-core/v4l2-ioctl.c
>> index 067dbdd0a9ef..0ee730aa6cc7 100644
>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>> @@ -1303,6 +1303,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc
>*fmt)
>>       case V4L2_PIX_FMT_Y6:           descr = "6-bit Greyscale"; break;
>>       case V4L2_PIX_FMT_Y10:          descr = "10-bit Greyscale"; break;
>>       case V4L2_PIX_FMT_Y12:          descr = "12-bit Greyscale"; break;
>> +     case V4L2_PIX_FMT_Y012:         descr = "12-bit Greyscale"; break;
>>       case V4L2_PIX_FMT_Y14:          descr = "14-bit Greyscale"; break;
>>       case V4L2_PIX_FMT_Y16:          descr = "16-bit Greyscale"; break;
>>       case V4L2_PIX_FMT_Y16_BE:       descr = "16-bit Greyscale BE"; break;
>> diff --git a/include/uapi/linux/videodev2.h
>> b/include/uapi/linux/videodev2.h index 5448aa3b7858..3d8f89bff33c
>> 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -583,6 +583,7 @@ struct v4l2_pix_format {
>>  #define V4L2_PIX_FMT_Y6      v4l2_fourcc('Y', '0', '6', ' ') /*  6  Greyscale     */
>>  #define V4L2_PIX_FMT_Y10     v4l2_fourcc('Y', '1', '0', ' ') /* 10  Greyscale
>*/
>>  #define V4L2_PIX_FMT_Y12     v4l2_fourcc('Y', '1', '2', ' ') /* 12  Greyscale
>*/
>> +#define V4L2_PIX_FMT_Y012    v4l2_fourcc('Y', '0', '1', '2') /* 12  Greyscale
>*/
>>  #define V4L2_PIX_FMT_Y14     v4l2_fourcc('Y', '1', '4', ' ') /* 14  Greyscale
>*/
>>  #define V4L2_PIX_FMT_Y16     v4l2_fourcc('Y', '1', '6', ' ') /* 16  Greyscale
>*/
>>  #define V4L2_PIX_FMT_Y16_BE  v4l2_fourcc_be('Y', '1', '6', ' ') /* 16
>> Greyscale BE  */