Hello
On Mon, Feb 12, 2024 at 11:58:32AM +0000, Dave Stevenson wrote:
> On Fri, 9 Feb 2024 at 21:15, Nicolas Dufresne <nicolas@xxxxxxxxxxxx> wrote:
> >
> > Le vendredi 09 février 2024 à 19:28 +0000, Dave Stevenson a écrit :
> > > 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.
> > >
I now wonder why creating two new files instead of adding Y12P and
Y14P to the table of luma-only formats we have in the above mentioned
file.
In the notes at the bottom of the page we can indeed report that the P
variants of the Y10 Y12 and Y14 formats are packed according to the
MIPI CSI-2 specification, even if, as Dave said, this is a pretty
standard convention for the educated readers of the v4l2 spec.
In facts, this is what has been done already for the existing luma
formats in:
af4f45057695 ("media: doc: pixfmt-yuv: Move all luma-only YUV formats to common file")
So I guess it's correct to keep expanding the existing file instead of
adding new ones. Sorry for not having realized it earlier.
> > > 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 :)
> >
> > A bit sad, but what can we do, I keep missing patches ;-P
>
> Not recently though.
>
> V4L2_PIX_FMT_Y10P was added in July 2018. [1]
> The use of V4L2_PIX_FMT_Sxxxx10P for Bayer format MIPI 10 bit packing
> was added in Dec 2014 [2]
>
> Dave
>
> [1] 6e15bec49f36 media: v4l: Add new 10-bit packed grayscale format
> [2] 4353e36ee84d [media] v4l: Add packed Bayer raw10 pixel formats
>
> > Nicolas
> >
> > >
> > > 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 */
> > > >
> >
