On 02/11/2020 23:40, Laurent Pinchart wrote:
> Add three new pixel formats that store RGB data in BGR order with 10, 12
> and 16 bits per component. They are used by the Xilinx Video Frame
> Buffer Read/Write IP cores.
>
> The nomenclature for these new formats follows the 8- and 16-bpp RGB
> formats and the DRM format naming conventions, which differs from the
> 24- and 32-bpp RGB formats in V4L2.
>
> As the number of bits per pixel grows quite large, a table with one
> column per bit would be difficult to read. These formats are thus
> described with one column per byte.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> Changes since v1:
>
> - Interleave component names and number of bits
> ---
> .../userspace-api/media/v4l/pixfmt-rgb.rst | 69 +++++++++++++++++++
> include/uapi/linux/videodev2.h | 5 ++
> 2 files changed, 74 insertions(+)
>
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst b/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst
> index 405d6f032078..846d307624fc 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst
> @@ -1079,6 +1079,75 @@ order of components as seen in a 24- or 32-bit little endian word.
> \endgroup
>
>
> +More Than 8 Bits Per Component
> +==============================
> +
> +These formats store an RGB triplet in four bytes or more. Similarly to the 8-
> +and 16-bpp formats, they are named based on the order of the RGB components as
> +seen in a word, which is then stored in memory in little endian byte order, and
> +on the number of bits for each component. The component names and the
> +corresponding number of bits are interleaved for clarity.
> +
> +.. raw:: latex
> +
> + \begingroup
> + \tiny
> + \setlength{\tabcolsep}{2pt}
> +
> +.. tabularcolumns:: |p{2.8cm}|p{2.0cm}|p{2.0cm}|p{2.0cm}|p{2.0cm}|p{2.0cm}|p{2.0cm}|p{2.0cm}|
> +
> +
> +.. flat-table:: RGB Formats With More Than 8 Bits Per Component
> + :stub-columns: 0
> +
> + * - Identifier
> + - Code
> + - Byte 0 in memory
> + - Byte 1
> + - Byte 2
> + - Byte 3
> + - Byte 4
> + - Byte 5
> + * .. _V4L2-PIX-FMT-X2B10G10R10:
> +
> + - ``V4L2_PIX_FMT_X2B10G10R10``
> + - 'XB30'
> +
> + - R\ :sub:`7-0`
> + - G\ :sub:`5-0` R\ :sub:`9-8`
> + - B\ :sub:`3-0` G\ :sub:`9-6`
> + - `-`\ :sub:`1-0` B\ :sub:`9-4`
Hmm, this is hard to read and understand.
The problem here is the use of '-' to indicate padding (unused) bits.
I was wondering whether it wouldn't be clearer to replace '-' by 'x' (for
an unused bit) or 'X' (for an unused byte) throughout these docs.
So this then becomes: X\ :sub:`1-0`.
It would also nicely correspond to the use of 'X' in the format name.
Regards,
Hans
> +
> + -
> + * .. _V4L2-PIX-FMT-X4B12G12R12:
> +
> + - ``V4L2_PIX_FMT_X4B12G12R12``
> + - 'XB36'
> +
> + - R\ :sub:`7-0`
> + - G\ :sub:`3-0` R\ :sub:`11-8`
> + - G\ :sub:`11-4`
> + - B\ :sub:`7-0`
> + - `-`\ :sub:`3-0` B\ :sub:`11-8`
> +
> + -
> + * .. _V4L2-PIX-FMT-B16G16R16:
> +
> + - ``V4L2_PIX_FMT_B16G16R16``
> + - 'XB48'
> +
> + - R\ :sub:`7-0`
> + - R\ :sub:`15-8`
> + - G\ :sub:`7-0`
> + - G\ :sub:`15-8`
> + - B\ :sub:`7-0`
> + - B\ :sub:`15-8`
> +
> +.. raw:: latex
> +
> + \endgroup
> +
> +
> Deprecated RGB Formats
> ======================
>
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 54b9fe3b7636..fab1dbb1a618 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -558,6 +558,11 @@ struct v4l2_pix_format {
> #define V4L2_PIX_FMT_ARGB32 v4l2_fourcc('B', 'A', '2', '4') /* 32 ARGB-8-8-8-8 */
> #define V4L2_PIX_FMT_XRGB32 v4l2_fourcc('B', 'X', '2', '4') /* 32 XRGB-8-8-8-8 */
>
> +/* RGB formats (more than 8 bits per component) */
> +#define V4L2_PIX_FMT_X2B10G10R10 v4l2_fourcc('X', 'B', '3', '0') /* 32 XBGR-2-10-10-10 */
> +#define V4L2_PIX_FMT_X4B12G12R12 v4l2_fourcc('X', 'B', '3', '6') /* 40 XBGR-4-12-12-12 */
> +#define V4L2_PIX_FMT_B16G16R16 v4l2_fourcc('X', 'B', '4', '8') /* 48 BGR-16-16-16 */
> +
> /* Grey formats */
> #define V4L2_PIX_FMT_GREY v4l2_fourcc('G', 'R', 'E', 'Y') /* 8 Greyscale */
> #define V4L2_PIX_FMT_Y4 v4l2_fourcc('Y', '0', '4', ' ') /* 4 Greyscale */
>
