Re: [PATCH v5 1/3] media: videodev2: Add flag to unconditionnaly enumerate pixels formats

[Benjamin Gaignard]

Le 30/07/2024 à 09:08, Hans Verkuil a écrit :
> On 22/07/2024 17:05, Benjamin Gaignard wrote:
> > When the index field is ORed with V4L2_FMT_FLAG_ENUM_ALL the driver
> > will ignore any configuration and enumerate all the possible formats.
> > Drivers which do not support this flag yet always return an EINVAL
> > error code.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> > ---
> > changes in version 5:
> > - Reset the proposal to follow Hans's advices
> > - Add new flag to be used with index field.
> >
> >   .../userspace-api/media/v4l/vidioc-enum-fmt.rst      | 12 +++++++++++-
> >   .../userspace-api/media/videodev2.h.rst.exceptions   |  1 +
> >   include/uapi/linux/videodev2.h                       |  3 +++
> >   3 files changed, 15 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..12e1e65e6a71 100644
> > --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> > +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> > @@ -85,7 +85,11 @@ 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
> You need to start a new paragraph before 'When'. Otherwise you might read
> that the 'When' sentence is somehow related to the previous sentence.
>
> > +        index is ORed with V4L2_FMT_FLAG_ENUM_ALL the driver will ignore
> > +        any configuration and enumerate all the possible formats. Drivers
> I'd rephrase this a little bit:
>
> the driver will enumerate all the possible formats, ignoring any limitations
> from the current configuration.
>
> And after that I would like to see an example of a use-case.
>
> > +        which do not support this flag yet always return an ``EINVAL``
> > +        error code.
> >       * - __u32
> >         - ``type``
> >         - Type of the data stream, set by the application. Only these types
> > @@ -234,6 +238,12 @@ 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_FMT_FLAG_ENUM_ALL``
> I am not really happy with this name since the prefix is identical to that
> of other V4L2_FMT_FLAG_ defines. How about: V4L2_FMTDESC_FLAG_ENUM_ALL?
> Or V4L2_FMT_IDX_ENUM_ALL?

I will use V4L2_FMTDESC_FLAG_ENUM_ALL in the next version.

Regards,
Benjamin

> > +      - 0x80000000
> > +      - When the applications ORs ``index`` with ``V4L2_FMT_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
> > +        yet always return ``EINVAL``.
> >   
> >   Return Value
> >   ============
> > diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > index bdc628e8c1d6..8dc10a500fc6 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_FMT_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..3d11f91273a1 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_FMT_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
> Regards,
>
> 	Hans