linux-kernel - Re: [PATCH v7 1/3] media: videodev2: Add flag to unconditionally enumerate pixel formats

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Message-ID: <3017b1e4-ffa6-4601-b844-0e6f7d95a475@collabora.com>
Date: Mon, 14 Oct 2024 09:07:02 +0200
From: Benjamin Gaignard <benjamin.gaignard@...labora.com>
To: Hans Verkuil <hverkuil-cisco@...all.nl>, mchehab@...nel.org,
 ezequiel@...guardiasur.com.ar
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-rockchip@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v7 1/3] media: videodev2: Add flag to unconditionally
 enumerate pixel formats


Le 11/10/2024 à 15:29, Hans Verkuil a écrit :
> Hi Benjamin,
>
> On 26/08/2024 19:24, Benjamin Gaignard wrote:
>> When the index is ORed with V4L2_FMTDESC_FLAG_ENUM_ALL the
>> driver clears the flag and enumerate all the possible formats,
>> ignoring any limitations from the current configuration.
>> Drivers which do not support this flag yet always return an EINVAL.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>> ---
>> change in version 7:
>> - Rework documentation about which drivers should use the flag
>>
>>   .../media/v4l/vidioc-enum-fmt.rst              | 18 +++++++++++++++++-
>>   .../media/videodev2.h.rst.exceptions           |  1 +
>>   include/uapi/linux/videodev2.h                 |  3 +++
>>   3 files changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> index 3adb3d205531..e39c87bcbfc3 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> @@ -85,7 +85,17 @@ the ``mbus_code`` field is handled differently:
>>       * - __u32
>>         - ``index``
>>         - Number of the format in the enumeration, set by the application.
>> -	This is in no way related to the ``pixelformat`` field.
>> +        This is in no way related to the ``pixelformat`` field.
>> +        When the index is ORed with ``V4L2_FMTDESC_FLAG_ENUM_ALL`` the
>> +        driver clears the flag and enumerates all the possible formats,
>> +        ignoring any limitations from the current configuration. Drivers
>> +        which do not support this flag always return an ``EINVAL``
>> +        error code.
> I would like to add: " without clearing this flag."
>
>> +        Formats enumerated when using ``V4L2_FMTDESC_FLAG_ENUM_ALL`` flag
>> +        shouldn't be used when calling :c:func:`VIDIOC_ENUM_FRAMESIZES`
>> +        or :c:func:`VIDIOC_ENUM_FRAMEINTERVALS`.
>> +        ``V4L2_FMTDESC_FLAG_ENUM_ALL`` should only be used by drivers that
>> +        can return different format list depending on this flag.
>>       * - __u32
>>         - ``type``
>>         - Type of the data stream, set by the application. Only these types
>> @@ -234,6 +244,12 @@ the ``mbus_code`` field is handled differently:
>>   	valid. The buffer consists of ``height`` lines, each having ``width``
>>   	Data Units of data and the offset (in bytes) between the beginning of
>>   	each two consecutive lines is ``bytesperline``.
>> +    * - ``V4L2_FMTDESC_FLAG_ENUM_ALL``
>> +      - 0x80000000
>> +      - When the applications ORs ``index`` with ``V4L2_FMTDESC_FLAG_ENUM_ALL`` flag
>> +        the driver enumerates all the possible pixel formats without taking care
>> +        of any already set configuration. Drivers which do not support this flag,
>> +        always return ``EINVAL``.
> Ditto.
>
> If you agree, then I can make that change myself, no need to post a new version.

Of I agree :-)

Thanks a lot.
Benjamin

>
> Regards,
>
> 	Hans
>
>>   
>>   Return Value
>>   ============
>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> index bdc628e8c1d6..0a9ea9686c24 100644
>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> @@ -216,6 +216,7 @@ replace define V4L2_FMT_FLAG_CSC_YCBCR_ENC fmtdesc-flags
>>   replace define V4L2_FMT_FLAG_CSC_HSV_ENC fmtdesc-flags
>>   replace define V4L2_FMT_FLAG_CSC_QUANTIZATION fmtdesc-flags
>>   replace define V4L2_FMT_FLAG_META_LINE_BASED fmtdesc-flags
>> +replace define V4L2_FMTDESC_FLAG_ENUM_ALL fmtdesc-flags
>>   
>>   # V4L2 timecode types
>>   replace define V4L2_TC_TYPE_24FPS timecode-type
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 4e91362da6da..421a30cb0c51 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -904,6 +904,9 @@ struct v4l2_fmtdesc {
>>   #define V4L2_FMT_FLAG_CSC_QUANTIZATION		0x0100
>>   #define V4L2_FMT_FLAG_META_LINE_BASED		0x0200
>>   
>> +/*  Format description flag, to be ORed with the index */
>> +#define V4L2_FMTDESC_FLAG_ENUM_ALL		0x80000000
>> +
>>   	/* Frame Size and frame rate enumeration */
>>   /*
>>    *	F R A M E   S I Z E   E N U M E R A T I O N
>