linux-kernel - Re: [PATCH v5 05/10] media: v4l: Add definition for the Aspeed JPEG format

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Date:   Fri, 19 Nov 2021 17:37:47 +0800
From:   Jammy Huang <jammy_huang@...eedtech.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
CC:     "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "andrew@...id.au" <andrew@...id.au>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "eajames@...ux.ibm.com" <eajames@...ux.ibm.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "laurent.pinchart@...asonboard.com" 
        <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v5 05/10] media: v4l: Add definition for the Aspeed JPEG
 format

Dear Paul,

OK, thanks for your suggestion.

On 2021/11/19 下午 04:39, Paul Menzel wrote:
> Dear Jammy,
>
>
> Am 19.11.21 um 03:02 schrieb Jammy Huang:
>
>> On 2021/11/18 下午 08:33, Sakari Ailus wrote:
>>> On Thu, Nov 18, 2021 at 03:40:26PM +0800, Jammy Huang wrote:
>>>> This introduces support for the Aspeed JPEG format, where the new frame
>>>> can refer to previous frame to reduce the amount of compressed data. The
>>>> concept is similar to I/P frame of video compression. I will compare the
>>>> new frame with previous one to decide which macroblock's data is
>>>> changed, and only the changed macroblocks will be compressed.
>>>>
>>>> This Aspeed JPEG format is used by the video engine on Aspeed platforms,
>>>> which is generally adapted for remote KVM.
>>>>
>>>> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
>>>> ---
>>>> v5:
>>>>     - no update
>>>> v4:
>>>>     - new
>>>> ---
>>>>    Documentation/media/uapi/v4l/pixfmt-reserved.rst | 12 ++++++++++++
>>>>    drivers/media/v4l2-core/v4l2-ioctl.c             |  1 +
>>>>    include/uapi/linux/videodev2.h                   |  1 +
>>>>    3 files changed, 14 insertions(+)
>>>>
>>>> diff --git a/Documentation/media/uapi/v4l/pixfmt-reserved.rst
>>>> b/Documentation/media/uapi/v4l/pixfmt-reserved.rst
>>>> index b2cd155e691b..23c05063133d 100644
>>>> --- a/Documentation/media/uapi/v4l/pixfmt-reserved.rst
>>>> +++ b/Documentation/media/uapi/v4l/pixfmt-reserved.rst
>>>> @@ -264,6 +264,18 @@ 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-AJPG:
>>>> +
>>>> +      - ``V4L2_PIX_FMT_AJPG``
>>>> +      - 'AJPG'
>>>> +      - ASPEED JPEG format used by the aspeed-video driver on Aspeed platforms,
>>>> +        which is generally adapted for remote KVM.
>>>> +        On each frame compression, I will compare the new frame with previous
>>>> +        one to decide which macroblock's data is changed, and only the changed
>>>> +        macroblocks will be compressed.
>>>> +
>>>> +        You could reference to chapter 36, Video Engine, of AST2600's datasheet
>>>> +        for more information.
>>> Is this datasheet publicly available? Do you have a URL?
>> Sorry, this datasheet is not publicly available.
>> Hans mentioned this as well in the discussion below:
>>
>> https://lkml.org/lkml/2021/11/10/101
> If questions come up during review, please also add the answers to the
> commit message of the next iteration. ;-) Maybe:
>
>> The implementation is based on datasheet *Name goes here*, revision
>> X, which is not publicly available.
> Kind regards,
>
> Paul

-- 
Best Regards
Jammy