On 7/17/24 15:14, Benjamin Gaignard wrote:
> Add new flags to enumerate all pixels formats when calling VIDIOC_ENUM_FMT ioctl.
> When this V4L2_FMT_FLAG_ENUM_ALL_FORMATS flag is set drivers must
> ignore the configuration and return the hardware supported pixel
> formats for the specified queue.
> To distinguish this particular enumeration case V4L2_FMT_FLAG_ALL_FORMATS
> flag must be set by the drivers to highlight support of this feature
> to user space applications.
> This will permit to discover which pixel formats are supported
> without setting codec-specific information so userland can more easily
> know if the driver suits its needs well.
> The main target are stateless decoders so update the documentation
> about how to use this flag.
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
> changes in version 4:
> - Explicitly document that the new flags are targeting mem2mem devices.
>
> .../userspace-api/media/v4l/dev-stateless-decoder.rst | 6 ++++++
> .../userspace-api/media/v4l/vidioc-enum-fmt.rst | 11 +++++++++++
> .../userspace-api/media/videodev2.h.rst.exceptions | 2 ++
> drivers/media/v4l2-core/v4l2-ioctl.c | 3 +++
> include/uapi/linux/videodev2.h | 2 ++
> 5 files changed, 24 insertions(+)
>
> diff --git a/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst b/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
> index 35ed05f2695e..b0b657de910d 100644
> --- a/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
> @@ -58,6 +58,12 @@ Querying capabilities
> default values for these controls being used, and a returned set of formats
> that may not be usable for the media the client is trying to decode.
>
> + * If the ``V4L2_FMT_FLAG_ENUM_ALL_FORMATS`` flag is set the driver must enumerate
> + all the supported formats without taking care of codec-dependent controls
> + set on the ``OUTPUT`` queue. To indicate that the driver has take care of this
> + flag it must set ``V4L2_FMT_FLAG_ALL_FORMATS`` flag for each format while
> + enumerating.
> +
> 3. The client may use :c:func:`VIDIOC_ENUM_FRAMESIZES` to detect supported
> resolutions for a given format, passing desired pixel format in
> :c:type:`v4l2_frmsizeenum`'s ``pixel_format``.
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> index 3adb3d205531..15bc2f59c05a 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> @@ -234,6 +234,17 @@ 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_FORMATS``
> + - 0x0400
> + - Set by userland applications to enumerate all possible pixel formats
> + without taking care of any OUTPUT or CAPTURE queue configuration.
> + This flag is relevant only for mem2mem devices.
> + * - ``V4L2_FMT_FLAG_ALL_FORMATS``
> + - 0x0800
> + - Set by the driver to indicated that format have been enumerated because
> + :ref:`V4L2_FMT_FLAG_ENUM_ALL_FORMATS <v4l2-pix-fmt-flag-set-csc>` has
> + been set by the userland application.
> + This flag is relevant only for mem2mem devices.
>
> Return Value
> ============
> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> index bdc628e8c1d6..7a3a1e9dc055 100644
> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> @@ -216,6 +216,8 @@ 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_FORMATS fmtdesc-flags
> +replace define V4L2_FMT_FLAG_ALL_FORMATS fmtdesc-flags
>
> # V4L2 timecode types
> replace define V4L2_TC_TYPE_24FPS timecode-type
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 4c76d17b4629..5785a98b6ba2 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1569,6 +1569,7 @@ static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
> int ret = check_fmt(file, p->type);
> u32 mbus_code;
> u32 cap_mask;
> + u32 flags;
>
> if (ret)
> return ret;
> @@ -1578,8 +1579,10 @@ static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
> p->mbus_code = 0;
>
> mbus_code = p->mbus_code;
> + flags = p->flags & V4L2_FMT_FLAG_ENUM_ALL_FORMATS;
Nacked-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Sorry, you can't just change a read-only field (i.e. set by the driver) to
something that can be set by the application as well. That can easily cause
problems: e.g. applications that leave the flags field uninitialized.
I will try to look at alternatives tomorrow, but this approach is definitely
a no-go.
Regards,
Hans
> memset_after(p, 0, type);
> p->mbus_code = mbus_code;
> + p->flags = flags;
>
> switch (p->type) {
> case V4L2_BUF_TYPE_VIDEO_CAPTURE:
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index fe6b67e83751..b6a5da79ba21 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -886,6 +886,8 @@ struct v4l2_fmtdesc {
> #define V4L2_FMT_FLAG_CSC_HSV_ENC V4L2_FMT_FLAG_CSC_YCBCR_ENC
> #define V4L2_FMT_FLAG_CSC_QUANTIZATION 0x0100
> #define V4L2_FMT_FLAG_META_LINE_BASED 0x0200
> +#define V4L2_FMT_FLAG_ENUM_ALL_FORMATS 0x0400
> +#define V4L2_FMT_FLAG_ALL_FORMATS 0x0800
>
> /* Frame Size and frame rate enumeration */
> /*
