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

[Hans Verkuil]

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@xxxxxxxxxxxxx>
> ---
> 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.

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