Re: [PATCH/RFC 16/16] media: v4l2: Add 10- and 12-bpc luma-only formats with linear packing

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Hi Nicolas,

On Thu, Sep 24, 2020 at 02:27:58PM -0400, Nicolas Dufresne wrote:
> Le mercredi 23 septembre 2020 à 05:43 +0300, Laurent Pinchart a écrit :
> > Add two new formats storing luma only in 10- and 12-bpc variants, with
> > linear packing. They are used by the Xilinx Video Frame Buffer
> > Read/Write IP cores.
> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > ---
> >  .../media/v4l/pixfmt-yuv-luma.rst             | 23 +++++++++++++++++++
> >  include/uapi/linux/videodev2.h                |  2 ++
> >  2 files changed, 25 insertions(+)
> > 
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
> > index b24947b52cf8..3e2a7af5ed67 100644
> > --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv-luma.rst
> > @@ -24,6 +24,7 @@ are often referred to as greyscale formats.
> >     - Y'\ :sub:`x`\ [9:2] denotes bits 9 to 2 of the Y' value for pixel at colum
> >       `x`.
> >     - `0` denotes padding bits set to 0.
> > +   - `-` denotes padding bits with undefined values.
> >  
> >  
> >  .. flat-table:: Luma-Only Image Formats
> > @@ -82,6 +83,17 @@ are often referred to as greyscale formats.
> >        - Y'\ :sub:`3`\ [9:2]
> >        - Y'\ :sub:`3`\ [1:0] Y'\ :sub:`2`\ [1:0] Y'\ :sub:`1`\ [1:0] Y'\ :sub:`0`\ [1:0]
> >  
> > +    * .. _V4L2-PIX-FMT-Y10X:
> 
> That's interesting, you are using a different convention here. If I
> refer to the XYUV_2101010 one, usign that convention instead would be
> XY10X10V10. It's not much more readable, and you have to deduce the 2
> bits, just like you have to deduce that X here is 6bits. Perhaps we can
> find a compromises that makes it consistent ? YX_10_2 ?

I'm not sure to follow you. This is a greyscale format, it only stores
the luma component, so XY10X10V10 doesn't match (and I assume you meant
XY10U10V10).

> > +
> > +      - ``V4L2_PIX_FMT_Y10X``
> > +      - 'Y10X'
> > +
> > +      - Y'\ :sub:`0`\ [7:0]
> > +      - Y'\ :sub:`1`\ [5:0] Y'\ :sub:`0`\ [9:8]
> > +      - Y'\ :sub:`2`\ [3:0] Y'\ :sub:`1`\ [9:6]
> > +      - `- -` Y'\ :sub:`2`\ [9:4]
> > +      - ...
> > +
> >      * .. _V4L2-PIX-FMT-Y12:
> >  
> >        - ``V4L2_PIX_FMT_Y12``
> > @@ -93,6 +105,17 @@ are often referred to as greyscale formats.
> >        - ...
> >        - ...
> >  
> > +    * .. _V4L2-PIX-FMT-Y12X:
> > +
> > +      - ``V4L2_PIX_FMT_Y12X``
> > +      - 'Y12X'
> > +
> > +      - Y'\ :sub:`0`\ [7:0]
> > +      - Y'\ :sub:`1`\ [3:0] Y'\ :sub:`0`\ [11:8]
> > +      - Y'\ :sub:`1`\ [11:4]
> > +      - Y'\ :sub:`2`\ [7:0]
> > +      - `- - - -` Y'\ :sub:`2`\ [11:8]
> > +
> >      * .. _V4L2-PIX-FMT-Y14:
> >  
> >        - ``V4L2_PIX_FMT_Y14``
> > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > index 9b4cab651df7..3d137a020cdb 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -579,6 +579,8 @@ 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_Y10X    v4l2_fourcc('Y', '1', '0', 'X') /* 10  Greyscale, 3 pixels in 4 bytes */
> > +#define V4L2_PIX_FMT_Y12X    v4l2_fourcc('Y', '1', '2', 'X') /* 12  Greyscale, 4 pixels in 5 bytes */
> >  
> >  /* Palette formats */
> >  #define V4L2_PIX_FMT_PAL8    v4l2_fourcc('P', 'A', 'L', '8') /*  8  8-bit palette */
> 

-- 
Regards,

Laurent Pinchart



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