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

[Benjamin Gaignard]

Le 30/07/2024 à 09:19, Hans Verkuil a écrit :
> On 30/07/2024 09:08, Hans Verkuil wrote:
> > 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.
> Should the flag be kept on return of VIDIOC_ENUM_FMT or should it be cleared?
> For reference: VIDIOC_QUERYCTRL will clear the V4L2_CTRL_FLAG_NEXT_CTRL flag.
>
> Regardless of what we pick, it should be documented.

I believe most of the flags are cleared in v4l2 so I will to do the same and
document it.

> Regards,
>
> 	Hans
>
> > > +        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?
> >
> > > +      - 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