linux-kernel - Re: [PATCH 2/2] [media] v4l: Add 10-bits per channel YUV pixel formats

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Date:   Mon, 2 Jan 2017 21:03:58 +0800
From:   ayaka <ayaka@...lik.info>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     dri-devel@...ts.freedesktop.org, daniel.vetter@...el.com,
        jani.nikula@...ux.intel.com, seanpaul@...omium.org,
        airlied@...ux.ie, linux-kernel@...r.kernel.org,
        randy.li@...k-chips.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, laurent.pinchart@...asonboard.com
Subject: Re: [PATCH 2/2] [media] v4l: Add 10-bits per channel YUV pixel
 formats



On 01/02/2017 07:07 PM, Sakari Ailus wrote:
> Hi,
>
> On Mon, Jan 02, 2017 at 06:53:16PM +0800, ayaka wrote:
>>
>> On 01/02/2017 05:10 PM, Sakari Ailus wrote:
>>> Hi Randy,
>>>
>>> Thanks for the patch.
>>>
>>> On Mon, Jan 02, 2017 at 04:50:04PM +0800, Randy Li wrote:
>>>> The formats added by this patch are:
>>>> 	V4L2_PIX_FMT_P010
>>>> 	V4L2_PIX_FMT_P010M
>>>> Currently, none of driver uses those format, but some video device
>>>> has been confirmed with could as those format for video output.
>>>> The Rockchip's new decoder has supported those format for profile_10
>>>> HEVC/AVC video.
>>>>
>>>> Signed-off-by: Randy Li <ayaka@...lik.info>
>>> If the format resembles the existing formats but on a different bit depth,
>>> it should be named in similar fashion.
>> Do you mean it would be better if it is called as NV12_10?
> If it otherwise resembles NV12 but just has 10 bits per pixel, I think
> NV12_10 is a good name for it.
The main reason I don't like it is that there is a various of software 
having used the P010 for this kind of pixel format. It would leadi a 
conflict between them(and I never saw it is used as NV12_10), as the 
P010 is more common to be used.
I left a problem unsolved for P010 in v4l2, P010 have two variant, 
little endian and big endian. Which could be easy identified in drm 
driver(there is a flag for all the big endian pixel format).
>
>>> Could you also add ReST documentation for the format, please?
>> I will.
>>> The common requirement for merging patches that change interfaces has been
>>> that there's a user for that change. It'll still help you to get this
>> The kernel used in rockchip has supported that format in drm driver, but
>> just we don't have a agreement about the pixel format. As the Gstreamer and
>> some others would call it with a P010_ prefix, but Mark(rockchip's drm
>> author) prefer the something like NV12_10, that is why I sent out those
>> patches, I want the upstream decided its final name.
> Ack.
>
> I think we haven't really tried to unify the format naming in the past
> between the two subsystems. If existing conventions exist on both regarding
> this format, then it's probably better to follow those.
>
> Cc Laurent as well.
>
>>> reviewed now so the interface that the future hopefully-in-mainline driver
>>> provides will not change.
>>>
>>>> ---
>>>>   include/uapi/linux/videodev2.h | 2 ++
>>>>   1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>>> index 46e8a2e3..9e03f20 100644
>>>> --- a/include/uapi/linux/videodev2.h
>>>> +++ b/include/uapi/linux/videodev2.h
>>>> @@ -551,6 +551,7 @@ struct v4l2_pix_format {
>>>>   #define V4L2_PIX_FMT_NV61    v4l2_fourcc('N', 'V', '6', '1') /* 16  Y/CrCb 4:2:2  */
>>>>   #define V4L2_PIX_FMT_NV24    v4l2_fourcc('N', 'V', '2', '4') /* 24  Y/CbCr 4:4:4  */
>>>>   #define V4L2_PIX_FMT_NV42    v4l2_fourcc('N', 'V', '4', '2') /* 24  Y/CrCb 4:4:4  */
>>>> +#define V4L2_PIX_FMT_P010    v4l2_fourcc('P', '0', '1', '0') /* 15  Y/CbCr 4:2:0, 10 bits per channel */
>>>>   /* two non contiguous planes - one Y, one Cr + Cb interleaved  */
>>>>   #define V4L2_PIX_FMT_NV12M   v4l2_fourcc('N', 'M', '1', '2') /* 12  Y/CbCr 4:2:0  */
>>>> @@ -559,6 +560,7 @@ struct v4l2_pix_format {
>>>>   #define V4L2_PIX_FMT_NV61M   v4l2_fourcc('N', 'M', '6', '1') /* 16  Y/CrCb 4:2:2  */
>>>>   #define V4L2_PIX_FMT_NV12MT  v4l2_fourcc('T', 'M', '1', '2') /* 12  Y/CbCr 4:2:0 64x32 macroblocks */
>>>>   #define V4L2_PIX_FMT_NV12MT_16X16 v4l2_fourcc('V', 'M', '1', '2') /* 12  Y/CbCr 4:2:0 16x16 macroblocks */
>>>> +#define V4L2_PIX_FMT_P010M   v4l2_fourcc('P', 'M', '1', '0') /* 15  Y/CbCr 4:2:0, 10 bits per channel */
>>>>   /* three planes - Y Cb, Cr */
>>>>   #define V4L2_PIX_FMT_YUV410  v4l2_fourcc('Y', 'U', 'V', '9') /*  9  YUV 4:1:0     */