Hi Nicolas
On Fri, 9 Feb 2024 at 17:53, Nicolas Dufresne <nicolas@xxxxxxxxxxxx> wrote:
>
> Le vendredi 09 février 2024 à 17:48 +0100, Jacopo Mondi a écrit :
> > From: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> >
> > This is the format used by monochrome 12bit image sensors.
> >
> > Signed-off-by: Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx>
> > ---
> > .../userspace-api/media/v4l/pixfmt-y12p.rst | 38 +++++++++++++++++++
> > .../userspace-api/media/v4l/yuv-formats.rst | 1 +
> > drivers/media/v4l2-core/v4l2-ioctl.c | 1 +
> > include/uapi/linux/videodev2.h | 1 +
> > 4 files changed, 41 insertions(+)
> > create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-y12p.rst
> >
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-y12p.rst b/Documentation/userspace-api/media/v4l/pixfmt-y12p.rst
> > new file mode 100644
> > index 000000000000..b2eb4a72724d
> > --- /dev/null
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-y12p.rst
> > @@ -0,0 +1,38 @@
> > +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> > +
> > +.. _V4L2-PIX-FMT-Y12P:
> > +
> > +******************************
> > +V4L2_PIX_FMT_Y12P ('Y12P')
> > +******************************
> > +
> > +Grey-scale image as a MIPI RAW12 packed array
> > +
> > +
> > +Description
> > +===========
> > +
> > +This is a packed grey-scale image format with a depth of 12 bits per
> > +pixel. Two consecutive pixels are packed into 3 bytes. The first 2 bytes
> > +contain the 8 high order bits of the pixels, and the 3rd byte contains the 4
> > +least significants bits of each pixel, in the same order.
>
> This is an interesting arrangement, which make me feel that Y12P is perhaps bit
> too generic ? Perhaps something like:
>
> V4L2_PIX_FMT_Y12_MIPI
>
> That being said, I don't mind if you reserve the nice and short name for the
> first occurrence of such format in 20 years (it might equally be the last). Will
> they do the same for Y10, by storing 4 bytes of higher 8bit of 4 pixels, and
> packing the remaining lower 2 bits packed in the fif bytes ? Cause for this one,
> we'd have confusion, since CODEC usually just place all the bits in order over 5
> bytes here (which have its own issues of course).
We already have V4L2_PIX_FMT_Y10P defined for the MIPI packing for
10bit luma-only.
https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/pixfmt-yuv-luma.html
This is only extending the definitions for the other bit depths using
the same pattern.
Adding the P is also the same pattern as for the Bayer formats -
V4L2_PIX_FMT_SRGGB10 for the 10bit unpacked to 16bit, and
V4L2_PIX_FMT_SRGGB10P for the MIPI packed variant.
I'm not inventing anything new here :)
Dave
> > +
> > +**Byte Order.**
> > +Each cell is one byte.
> > +
> > +.. tabularcolumns:: |p{2.2cm}|p{1.2cm}|p{1.2cm}|p{3.1cm}|
> > +
> > +
> > +.. flat-table::
> > + :header-rows: 0
> > + :stub-columns: 0
> > + :widths: 2 1 1 1
> > +
> > +
> > + - - start + 0:
> > + - Y'\ :sub:`00high`
> > + - Y'\ :sub:`01high`
> > + - Y'\ :sub:`01low`\ (bits 7--4)
> > +
> > + Y'\ :sub:`00low`\ (bits 3--0)
> > +
> > diff --git a/Documentation/userspace-api/media/v4l/yuv-formats.rst b/Documentation/userspace-api/media/v4l/yuv-formats.rst
> > index 24b34cdfa6fe..7c9ccfdd94cd 100644
> > --- a/Documentation/userspace-api/media/v4l/yuv-formats.rst
> > +++ b/Documentation/userspace-api/media/v4l/yuv-formats.rst
> > @@ -267,6 +267,7 @@ image.
> > pixfmt-packed-yuv
> > pixfmt-yuv-planar
> > pixfmt-yuv-luma
> > + pixfmt-y12p
> > pixfmt-y8i
> > pixfmt-y12i
> > pixfmt-uv8
> > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> > index 33076af4dfdb..483498c55899 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -1311,6 +1311,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
> > case V4L2_PIX_FMT_Y16_BE: descr = "16-bit Greyscale BE"; break;
> > case V4L2_PIX_FMT_Y10BPACK: descr = "10-bit Greyscale (Packed)"; break;
> > case V4L2_PIX_FMT_Y10P: descr = "10-bit Greyscale (MIPI Packed)"; break;
> > + case V4L2_PIX_FMT_Y12P: descr = "12-bit Greyscale (MIPI Packed)"; break;
> > case V4L2_PIX_FMT_IPU3_Y10: descr = "10-bit greyscale (IPU3 Packed)"; break;
> > case V4L2_PIX_FMT_Y8I: descr = "Interleaved 8-bit Greyscale"; break;
> > case V4L2_PIX_FMT_Y12I: descr = "Interleaved 12-bit Greyscale"; break;
> > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > index a8015e5e7fa4..11ebf9b22ccb 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -598,6 +598,7 @@ struct v4l2_pix_format {
> > /* Grey bit-packed formats */
> > #define V4L2_PIX_FMT_Y10BPACK v4l2_fourcc('Y', '1', '0', 'B') /* 10 Greyscale bit-packed */
> > #define V4L2_PIX_FMT_Y10P v4l2_fourcc('Y', '1', '0', 'P') /* 10 Greyscale, MIPI RAW10 packed */
> > +#define V4L2_PIX_FMT_Y12P v4l2_fourcc('Y', '1', '2', 'P') /* 12 Greyscale, MIPI RAW12 packed */
> > #define V4L2_PIX_FMT_IPU3_Y10 v4l2_fourcc('i', 'p', '3', 'y') /* IPU3 packed 10-bit greyscale */
> >
> > /* Palette formats */
>
