linux-kernel - Re: [PATCH 1/3] v4l: Add Qualcomm custom compressed pixel formats

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Date:   Wed, 2 Jun 2021 16:29:08 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-api@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH 1/3] v4l: Add Qualcomm custom compressed pixel formats



On 6/2/21 12:56 PM, Hans Verkuil wrote:
> On 29/04/2021 12:58, Stanimir Varbanov wrote:
>> Here we add custom Qualcomm raw compressed pixel formats. They are
>> used in Qualcomm SoCs to optimaize the interconnect bandwidth.
> 
> optimize
> 
>>
>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
>> ---
>>  .../userspace-api/media/v4l/pixfmt-reserved.rst      | 12 ++++++++++++
>>  drivers/media/v4l2-core/v4l2-ioctl.c                 |  2 ++
>>  include/uapi/linux/videodev2.h                       |  2 ++
>>  3 files changed, 16 insertions(+)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
>> index 0b879c0da713..30b9cef4cbf0 100644
>> --- a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
>> +++ b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
>> @@ -260,6 +260,18 @@ please make a proposal on the linux-media mailing list.
>>  	of tiles, resulting in 32-aligned resolutions for the luminance plane
>>  	and 16-aligned resolutions for the chrominance plane (with 2x2
>>  	subsampling).
>> +    * .. _V4L2-PIX-FMT-QC8C:
>> +
>> +      - ``V4L2_PIX_FMT_QC8C``
>> +      - 'QC8C'
>> +      - Compressed Macro-tile 8Bit YUV420 format used by Qualcomm platforms.
> 
> 8Bit -> 8-bit
> 
>> +	The compression is lossless. It contains four planes.
>> +    * .. _V4L2-PIX-FMT-QC10C:
>> +
>> +      - ``V4L2_PIX_FMT_QC10C``
>> +      - 'QC10C'
>> +      - Compressed Macro-tile 10Bit YUV420 format used by Qualcomm platforms.
> 
> 10Bit -> 10-bit
> 
>> +	The compression is lossless. It contains four planes.
> 
> What is not clear from this description is if these formats are opaque, i.e. the
> only way to decompress is through hardware, or if they can be decompressed in
> software. If so, a reference to Qualcomm documentation would be useful. See e.g.
> the V4L2_PIX_FMT_MT21C description (that's an opaque format).

Yes, the formats are opaque and can be decompressed by hardware blocks
only. I'll clear that in v2. Thanks for the review.

-- 
regards,
Stan