Re: [PATCH v3 08/10] media: v4l: Support line-based metadata capture

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Jacopo,

On Thu, Aug 10, 2023 at 05:24:14PM +0200, Jacopo Mondi wrote:
> Hi Sakari
> 
> On Tue, Aug 08, 2023 at 10:55:36AM +0300, Sakari Ailus wrote:
> > many camera sensors, among other devices, transmit embedded data and image
> > 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@linux.intel.com>
> > ---
> >  .../userspace-api/media/v4l/dev-meta.rst          | 15 +++++++++++++++
> >  .../userspace-api/media/v4l/vidioc-enum-fmt.rst   |  7 +++++++
> >  .../media/videodev2.h.rst.exceptions              |  1 +
> >  drivers/media/v4l2-core/v4l2-ioctl.c              |  5 +++--
> >  include/uapi/linux/videodev2.h                    | 10 ++++++++++
> >  5 files changed, 36 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/userspace-api/media/v4l/dev-meta.rst b/Documentation/userspace-api/media/v4l/dev-meta.rst
> > index 0e7e1ee1471a..4b24bae6e171 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 samples. Valid when :c:type`v4l2_fmtdesc`
> > +	flag ``V4L2_FMT_FLAG_META_LINE_BASED`` is set, otherwise zero. See
> > +	:c:func:`VIDIOC_ENUM_FMT`.
> > +    * - __u32
> > +      - ``height``
> > +      - Number of rows of metadata. Valid when :c:type`v4l2_fmtdesc` flag
> > +	``V4L2_FMT_FLAG_META_LINE_BASED`` is set, otherwise zero. See
> > +	:c:func:`VIDIOC_ENUM_FMT`.
> > +    * - __u32
> > +      - ``bytesperline``
> > +      - 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
> 
> Isn't ``width`` in samples ?

Indeed, it's better to refer to samples for clarity. I'll fix for v4.

I'll also add bytesperline is in bytes (and not in samples).

> 
> > +	lines is ``bytesperline``.
> >
> >  Return Value
> >  ============
> > diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > index 3e58aac4ef0b..bdc628e8c1d6 100644
> > --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > @@ -215,6 +215,7 @@ replace define V4L2_FMT_FLAG_CSC_XFER_FUNC fmtdesc-flags
> >  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
> >
> >  # 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 fbbddc333a30..971d784e7429 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -343,8 +343,9 @@ static void v4l_print_format(const void *arg, bool write_only)
> >  	case V4L2_BUF_TYPE_META_OUTPUT:
> >  		meta = &p->fmt.meta;
> >  		pixelformat = meta->dataformat;
> > -		pr_cont(", dataformat=%p4cc, buffersize=%u\n",
> > -			&pixelformat, meta->buffersize);
> > +		pr_cont(", dataformat=%p4cc, buffersize=%u, width=%u, height=%u, bytesperline=%u\n",
> > +			&pixelformat, meta->buffersize, meta->width,
> > +			meta->height, meta->bytesperline);
> >  		break;
> >  	}
> >  }
> > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > index b4284a564025..d26c0650c6a7 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -877,6 +877,7 @@ 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 */
> >  /*
> > @@ -2420,10 +2421,19 @@ 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
> 
> I'm a bit confused here as well, isn't width in samples ?

I'll change this one as well.

> 
> > + *			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));
> >
> >  /**

-- 
Kind regards,

Sakari Ailus