Hi Sakari,
Thank you for the patch.
On Sat, May 06, 2023 at 12:52:57AM +0300, Sakari Ailus wrote:
> many camera sensors, among other devices, transmit embedded data and image
s/many/Many/
> data for each CSI-2 frame. This embedded data typically contains register
> configuration of the sensor that has been used to capture the image data
> of the same frame.
>
> The embedded data is received by the CSI-2 receiver and has the same
> properties as the image data, including that it is line based: it has
> width, height and bytesperline (stride).
>
> Add these fields to struct v4l2_meta_format and document them.
>
> Also add V4L2_FMT_FLAG_META_LINE_BASED to tell a given format is
> line-based i.e. these fields of struct v4l2_meta_format are valid for it.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> ---
> .../userspace-api/media/v4l/dev-meta.rst | 15 +++++++++++++++
> .../userspace-api/media/v4l/vidioc-enum-fmt.rst | 7 +++++++
> include/uapi/linux/videodev2.h | 10 ++++++++++
> 3 files changed, 32 insertions(+)
>
> diff --git a/Documentation/userspace-api/media/v4l/dev-meta.rst b/Documentation/userspace-api/media/v4l/dev-meta.rst
> index 0e7e1ee1471a..7d3a64514db0 100644
> --- a/Documentation/userspace-api/media/v4l/dev-meta.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-meta.rst
> @@ -65,3 +65,18 @@ to 0.
> - ``buffersize``
> - Maximum buffer size in bytes required for data. The value is set by the
> driver.
> + * - __u32
> + - ``width``
> + - Width of a line of metadata in bytes. Valid when :c:type`v4l2_fmtdesc`
This departs from pixel formats, where the width is defined in pixels. I
wonder what the implications will be for userspace. Seeing one
implementation, both in a kernel driver and in libcamera, will help
validating the API.
> + flag ``V4L2_FMT_FLAG_META_LINE_BASED`` is set, otherwise zero. See
> + :c:func:`VIDIOC_ENUM_FMT`.
> + * - __u32
> + - ``height``
> + - Height of a line of metadata in bytes. Valid when :c:type`v4l2_fmtdesc`
The "height of a line" seems like a weird concept, especially if the
height is expressed in bytes. I assume this is a bad copy&paste.
> + flag ``V4L2_FMT_FLAG_META_LINE_BASED`` is set, otherwise zero. See
> + :c:func:`VIDIOC_ENUM_FMT`.
> + * - __u32
> + - ``bytesperlines``
> + - Offset in bytes between the beginning of two consecutive lines. Valid
> + when :c:type`v4l2_fmtdesc` flag ``V4L2_FMT_FLAG_META_LINE_BASED`` is
> + set, otherwise zero. See :c:func:`VIDIOC_ENUM_FMT`.
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> index 000c154b0f98..6d7664345a4e 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> @@ -227,6 +227,13 @@ the ``mbus_code`` field is handled differently:
> The application can ask to configure the quantization of the capture
> device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with
> :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set.
> + * - ``V4L2_FMT_FLAG_META_LINE_BASED``
> + - 0x0200
> + - The metadata format is line-based. In this case the ``width``,
> + ``height`` and ``bytesperline`` fields of :c:type:`v4l2_meta_format` are
> + valid. The buffer consists of ``height`` lines, each having ``width``
> + bytes of data and offset between the beginning of each two consecutive
> + lines is ``bytesperline``.
If we add width and height for metadata formats, does it mean that
drivers have to (or can) implement VIDIOC_ENUM_FRAMESIZES ? This should
be documented.
>
> Return Value
> ============
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index adcbdc15dcdb..3681b2c15901 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -873,6 +873,7 @@ struct v4l2_fmtdesc {
> #define V4L2_FMT_FLAG_CSC_YCBCR_ENC 0x0080
> #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
>
> /* Frame Size and frame rate enumeration */
> /*
> @@ -2407,10 +2408,19 @@ struct v4l2_sdr_format {
> * struct v4l2_meta_format - metadata format definition
> * @dataformat: little endian four character code (fourcc)
> * @buffersize: maximum size in bytes required for data
> + * @width: number of bytes of data per line (valid for line based
> + * formats only, see format documentation)
> + * @height: number of lines of data per buffer (valid for line based
> + * formats only)
> + * @bytesperline: offset between the beginnings of two adjacent lines in
> + * bytes (valid for line based formats only)
> */
> struct v4l2_meta_format {
> __u32 dataformat;
> __u32 buffersize;
> + __u32 width;
> + __u32 height;
> + __u32 bytesperline;
> } __attribute__ ((packed));
>
> /**
--
Regards,
Laurent Pinchart
