Re: [PATCH v9 06/46] media: uapi: v4l: Add generic 8-bit metadata format definitions

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Sakari,

Thank you for the patch.

On Tue, Apr 16, 2024 at 10:32:39PM +0300, Sakari Ailus wrote:
> Generic 8-bit metadata formats define the in-memory data layout but not
> the format of the data itself. The reasoning for having such formats is to
> allow CSI-2 receiver drivers to receive and DMA drivers to write the data
> to memory without knowing a large number of device-specific formats.
> 
> These formats may be used only in conjunction with a Media controller

"Media Controller" or "media controller"

> pipeline where the internal pad of the source sub-device defines the
> specific format of the data (using an mbus code).
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  .../userspace-api/media/v4l/dev-subdev.rst    |   2 +
>  .../userspace-api/media/v4l/meta-formats.rst  |   3 +-
>  .../media/v4l/metafmt-generic.rst             | 328 ++++++++++++++++++
>  drivers/media/v4l2-core/v4l2-ioctl.c          |   7 +
>  include/uapi/linux/videodev2.h                |   8 +
>  5 files changed, 347 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/userspace-api/media/v4l/metafmt-generic.rst
> 
> diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst
> index 43988516acdd..f375b820ab68 100644
> --- a/Documentation/userspace-api/media/v4l/dev-subdev.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst
> @@ -506,6 +506,8 @@ source pads.
>  
>      subdev-formats
>  
> +.. _subdev-routing:
> +
>  Streams, multiplexed media pads and internal routing
>  ----------------------------------------------------
>  
> diff --git a/Documentation/userspace-api/media/v4l/meta-formats.rst b/Documentation/userspace-api/media/v4l/meta-formats.rst
> index 0bb61fc5bc00..c23aac823d2c 100644
> --- a/Documentation/userspace-api/media/v4l/meta-formats.rst
> +++ b/Documentation/userspace-api/media/v4l/meta-formats.rst
> @@ -13,9 +13,10 @@ These formats are used for the :ref:`metadata` interface only.
>      :maxdepth: 1
>  
>      metafmt-d4xx
> +    metafmt-generic
>      metafmt-intel-ipu3
>      metafmt-rkisp1
>      metafmt-uvc
> +    metafmt-vivid
>      metafmt-vsp1-hgo
>      metafmt-vsp1-hgt
> -    metafmt-vivid
> diff --git a/Documentation/userspace-api/media/v4l/metafmt-generic.rst b/Documentation/userspace-api/media/v4l/metafmt-generic.rst
> new file mode 100644
> index 000000000000..cba34be64dfe
> --- /dev/null
> +++ b/Documentation/userspace-api/media/v4l/metafmt-generic.rst
> @@ -0,0 +1,328 @@
> +.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
> +
> +********************************************************************************************************************************************************************************************************************************************************************************
> +V4L2_META_FMT_GENERIC_8 ('MET8'), V4L2_META_FMT_GENERIC_CSI2_10 ('MC1A'), V4L2_META_FMT_GENERIC_CSI2_12 ('MC1C'), V4L2_META_FMT_GENERIC_CSI2_14 ('MC1E'), V4L2_META_FMT_GENERIC_CSI2_16 ('MC1G'), V4L2_META_FMT_GENERIC_CSI2_20 ('MC1K'), V4L2_META_FMT_GENERIC_CSI2_24 ('MC1O')
> +********************************************************************************************************************************************************************************************************************************************************************************
> +
> +
> +Generic line-based metadata formats
> +
> +
> +Description
> +===========
> +
> +These generic line-based metadata formats define the memory layout of the data
> +without defining the format or meaning of the metadata itself. These formats may
> +only be used with a Media Controller pipeline where the more specific format is
> +reported by an :ref:`internal sink pad <MEDIA-PAD-FL-INTERNAL>` of the source
> +sub-device. See also :ref:`source routes <subdev-routing>`.
> +
> +.. _v4l2-meta-fmt-generic-8:
> +
> +V4L2_META_FMT_GENERIC_8
> +-----------------------
> +
> +The V4L2_META_FMT_GENERIC_8 format is a plain 8-bit metadata format.
> +
> +This format is also used on CSI-2 for both 8 bits per ``Data Unit
> +<media-glossary-data-unit>`` as well as for 16 bits per Data Unit when two bytes
> +of metadata are packed into one 16-bit Data Unit.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_8.**
> +Each cell is one byte. "M" denotes a byte of metadata.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - M\ :sub:`10`
> +      - M\ :sub:`20`
> +      - M\ :sub:`30`
> +    * - start + 4:
> +      - M\ :sub:`01`
> +      - M\ :sub:`11`
> +      - M\ :sub:`21`
> +      - M\ :sub:`31`
> +
> +.. _v4l2-meta-fmt-generic-csi2-10:
> +
> +V4L2_META_FMT_GENERIC_CSI2_10
> +-----------------------------
> +
> +V4L2_META_FMT_GENERIC_CSI2_10 contains 8-bit generic metadata packed in 10-bit
> +Data Units, with one padding byte after every four bytes of metadata. This
> +format is typically used by CSI-2 receivers with a source that transmits
> +MEDIA_BUS_FMT_META_10 and the CSI-2 receiver writes the received data to memory
> +as-is.
> +
> +The packing of the data follows the MIPI CSI-2 specification and the padding of
> +the data is defined in the MIPI CCS specification.
> +
> +This format is also used in conjunction with 20 bits per ``Data Unit

s/in conjunction with/for/

Same below.

> +<media-glossary-data-unit>`` formats that pack two bytes of metadata into one
> +Data Unit.

How about adding a mention of MEDIA_BUS_FMT_META_20 here ? The CCS
specification calls this "RAW20 (with more optimal RAW10 packing)",
using the same vocabulary could help. Same for
V4L2_META_FMT_GENERIC_CSI2_12, and actually V4L2_META_FMT_GENERIC_8 too.

> +
> +This format is little endian.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_CSI2_10.**
> +Each cell is one byte. "M" denotes a byte of metadata and "x" a byte of padding.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{.8cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - M\ :sub:`10`
> +      - M\ :sub:`20`
> +      - M\ :sub:`30`
> +      - x
> +    * - start + 5:
> +      - M\ :sub:`01`
> +      - M\ :sub:`11`
> +      - M\ :sub:`21`
> +      - M\ :sub:`31`
> +      - x
> +
> +.. _v4l2-meta-fmt-generic-csi2-12:
> +
> +V4L2_META_FMT_GENERIC_CSI2_12
> +-----------------------------
> +
> +V4L2_META_FMT_GENERIC_CSI2_12 contains 8-bit generic metadata packed in 12-bit
> +Data Units, with two padding bytes after every four bytes of metadata. This

Isn't it one padding byte every two bytes of metadata ?

> +format is typically used by CSI-2 receivers with a source that transmits
> +MEDIA_BUS_FMT_META_12 and the CSI-2 receiver writes the received data to memory
> +as-is.
> +
> +The packing of the data follows the MIPI CSI-2 specification and the padding of
> +the data is defined in the MIPI CCS specification.
> +
> +This format is also used in conjunction with 24 bits per ``Data Unit
> +<media-glossary-data-unit>`` formats that pack two bytes of metadata into one
> +Data Unit.
> +
> +This format is little endian.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_CSI2_12.**
> +Each cell is one byte. "M" denotes a byte of metadata and "x" a byte of padding.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{.8cm}|p{.8cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - M\ :sub:`10`
> +      - x
> +      - M\ :sub:`20`
> +      - M\ :sub:`30`
> +      - x
> +    * - start + 6:
> +      - M\ :sub:`01`
> +      - M\ :sub:`11`
> +      - x
> +      - M\ :sub:`21`
> +      - M\ :sub:`31`
> +      - x
> +
> +.. _v4l2-meta-fmt-generic-csi2-14:
> +
> +V4L2_META_FMT_GENERIC_CSI2_14
> +-----------------------------
> +
> +V4L2_META_FMT_GENERIC_CSI2_14 contains 8-bit generic metadata packed in 14-bit
> +Data Units, with three padding bytes after every four bytes of metadata. This
> +format is typically used by CSI-2 receivers with a source that transmits
> +MEDIA_BUS_FMT_META_14 and the CSI-2 receiver writes the received data to memory
> +as-is.
> +
> +The packing of the data follows the MIPI CSI-2 specification and the padding of
> +the data is defined in the MIPI CCS specification.
> +
> +This format is little endian.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_CSI2_14.**
> +Each cell is one byte. "M" denotes a byte of metadata and "x" a byte of padding.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{1.2cm}|p{.8cm}|p{.8cm}|p{.8cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - M\ :sub:`10`
> +      - M\ :sub:`20`
> +      - M\ :sub:`30`
> +      - x
> +      - x
> +      - x
> +    * - start + 7:
> +      - M\ :sub:`01`
> +      - M\ :sub:`11`
> +      - M\ :sub:`21`
> +      - M\ :sub:`31`
> +      - x
> +      - x
> +      - x
> +
> +.. _v4l2-meta-fmt-generic-csi2-16:
> +
> +V4L2_META_FMT_GENERIC_CSI2_16
> +-----------------------------
> +
> +V4L2_META_FMT_GENERIC_CSI2_16 contains 8-bit generic metadata packed in 16-bit
> +Data Units, with one padding byte after every byte of metadata. This format is
> +typically used by CSI-2 receivers with a source that transmits
> +MEDIA_BUS_FMT_META_16 and the CSI-2 receiver writes the received data to memory
> +as-is.
> +
> +The packing of the data follows the MIPI CSI-2 specification and the padding of
> +the data is defined in the MIPI CCS specification.

Here you could also mention that more optimal packing schemes for
MEDIA_BUS_FMT_META_16 use V4L2_META_FMT_GENERIC_8. Same below.

> +
> +This format is little endian.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_CSI2_16.**
> +Each cell is one byte. "M" denotes a byte of metadata and "x" a byte of padding.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{1.2cm}|p{.8cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - x
> +      - M\ :sub:`10`
> +      - x
> +      - M\ :sub:`20`
> +      - x
> +      - M\ :sub:`30`
> +      - x
> +    * - start + 8:
> +      - M\ :sub:`01`
> +      - x
> +      - M\ :sub:`11`
> +      - x
> +      - M\ :sub:`21`
> +      - x
> +      - M\ :sub:`31`
> +      - x
> +
> +.. _v4l2-meta-fmt-generic-csi2-20:
> +
> +V4L2_META_FMT_GENERIC_CSI2_20
> +-----------------------------
> +
> +V4L2_META_FMT_GENERIC_CSI2_20 contains 8-bit generic metadata packed in 20-bit
> +Data Units, with alternating one or two padding bytes after every byte of
> +metadata. This format is typically used by CSI-2 receivers with a source that
> +transmits MEDIA_BUS_FMT_META_20 and the CSI-2 receiver writes the received data
> +to memory as-is.
> +
> +The packing of the data follows the MIPI CSI-2 specification and the padding of
> +the data is defined in the MIPI CCS specification.
> +
> +This format is little endian.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_CSI2_20.**
> +Each cell is one byte. "M" denotes a byte of metadata and "x" a byte of padding.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{.8cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8 8 8 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - x
> +      - M\ :sub:`10`
> +      - x
> +      - x
> +      - M\ :sub:`20`
> +      - x
> +      - M\ :sub:`30`
> +      - x
> +      - x
> +    * - start + 10:
> +      - M\ :sub:`01`
> +      - x
> +      - M\ :sub:`11`
> +      - x
> +      - x
> +      - M\ :sub:`21`
> +      - x
> +      - M\ :sub:`31`
> +      - x
> +      - x
> +
> +.. _v4l2-meta-fmt-generic-csi2-24:
> +
> +V4L2_META_FMT_GENERIC_CSI2_24
> +-----------------------------
> +
> +V4L2_META_FMT_GENERIC_CSI2_24 contains 8-bit generic metadata packed in 24-bit
> +Data Units, with two padding bytes after every byte of metadata. This format is
> +typically used by CSI-2 receivers with a source that transmits
> +MEDIA_BUS_FMT_META_24 and the CSI-2 receiver writes the received data to memory
> +as-is.
> +
> +The packing of the data follows the MIPI CSI-2 specification and the padding of
> +the data is defined in the MIPI CCS specification.
> +
> +This format is little endian.
> +
> +**Byte Order Of V4L2_META_FMT_GENERIC_CSI2_24.**
> +Each cell is one byte. "M" denotes a byte of metadata and "x" a byte of padding.
> +
> +.. tabularcolumns:: |p{2.4cm}|p{1.2cm}|p{.8cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{.8cm}|p{1.2cm}|p{.8cm}|p{.8cm}|
> +
> +.. flat-table:: Sample 4x2 Metadata Frame
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths: 12 8 8 8 8 8 8 8 8 8 8 8 8
> +
> +    * - start + 0:
> +      - M\ :sub:`00`
> +      - x
> +      - x
> +      - M\ :sub:`10`
> +      - x
> +      - x
> +      - M\ :sub:`20`
> +      - x
> +      - x
> +      - M\ :sub:`30`
> +      - x
> +      - x
> +    * - start + 12:
> +      - M\ :sub:`01`
> +      - x
> +      - x
> +      - M\ :sub:`11`
> +      - x
> +      - x
> +      - M\ :sub:`21`
> +      - x
> +      - x
> +      - M\ :sub:`31`
> +      - x
> +      - x
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 5aeff5519407..ae2dca7f2817 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1460,6 +1460,13 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
>  	case V4L2_PIX_FMT_Y210:		descr = "10-bit YUYV Packed"; break;
>  	case V4L2_PIX_FMT_Y212:		descr = "12-bit YUYV Packed"; break;
>  	case V4L2_PIX_FMT_Y216:		descr = "16-bit YUYV Packed"; break;
> +	case V4L2_META_FMT_GENERIC_8:	descr = "8-bit Generic Metadata"; break;
> +	case V4L2_META_FMT_GENERIC_CSI2_10:	descr = "8-bit Generic Meta, 10b CSI-2"; break;
> +	case V4L2_META_FMT_GENERIC_CSI2_12:	descr = "8-bit Generic Meta, 12b CSI-2"; break;
> +	case V4L2_META_FMT_GENERIC_CSI2_14:	descr = "8-bit Generic Meta, 14b CSI-2"; break;
> +	case V4L2_META_FMT_GENERIC_CSI2_16:	descr = "8-bit Generic Meta, 16b CSI-2"; break;
> +	case V4L2_META_FMT_GENERIC_CSI2_20:	descr = "8-bit Generic Meta, 20b CSI-2"; break;
> +	case V4L2_META_FMT_GENERIC_CSI2_24:	descr = "8-bit Generic Meta, 24b CSI-2"; break;
>  
>  	default:
>  		/* Compressed formats */
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 2663213b76a4..c7cf20b5da67 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -839,6 +839,14 @@ struct v4l2_pix_format {
>  #define V4L2_META_FMT_RK_ISP1_PARAMS	v4l2_fourcc('R', 'K', '1', 'P') /* Rockchip ISP1 3A Parameters */
>  #define V4L2_META_FMT_RK_ISP1_STAT_3A	v4l2_fourcc('R', 'K', '1', 'S') /* Rockchip ISP1 3A Statistics */
>  
> +#define V4L2_META_FMT_GENERIC_8		v4l2_fourcc('M', 'E', 'T', '8') /* Generic 8-bit metadata */
> +#define V4L2_META_FMT_GENERIC_CSI2_10	v4l2_fourcc('M', 'C', '1', 'A') /* 10-bit CSI-2 packed 8-bit metadata */
> +#define V4L2_META_FMT_GENERIC_CSI2_12	v4l2_fourcc('M', 'C', '1', 'C') /* 12-bit CSI-2 packed 8-bit metadata */
> +#define V4L2_META_FMT_GENERIC_CSI2_14	v4l2_fourcc('M', 'C', '1', 'E') /* 14-bit CSI-2 packed 8-bit metadata */
> +#define V4L2_META_FMT_GENERIC_CSI2_16	v4l2_fourcc('M', 'C', '1', 'G') /* 16-bit CSI-2 packed 8-bit metadata */
> +#define V4L2_META_FMT_GENERIC_CSI2_20	v4l2_fourcc('M', 'C', '1', 'K') /* 20-bit CSI-2 packed 8-bit metadata */
> +#define V4L2_META_FMT_GENERIC_CSI2_24	v4l2_fourcc('M', 'C', '1', 'O') /* 24-bit CSI-2 packed 8-bit metadata */
> +
>  /* priv field value to indicates that subsequent fields are valid. */
>  #define V4L2_PIX_FMT_PRIV_MAGIC		0xfeedcafe
>  

-- 
Regards,

Laurent Pinchart