Re: [PATCH 13/14] docs: admin-guide: media: bcm2835-isp: Add documentation for bcm2835-isp

Laurent Pinchart
2022-11-21T23:41:38Z

Hi Umang and Naush,

Thank you for the patch.

On Tue, Nov 22, 2022 at 03:17:21AM +0530, Umang Jain wrote:
> From: Naushir Patuck <naush@raspberrypi.com>
>
> Document device nodes, frame buffer formats and initial set of
> configuraiton that can be set from userspace to configure the pipeline.

s/configuraiton/configuration/

> Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> ---
> .../admin-guide/media/bcm2835-isp.rst | 127 ++++++++++++++++++
> .../userspace-api/media/drivers/index.rst | 1 +
> 2 files changed, 128 insertions(+)
> create mode 100644 Documentation/admin-guide/media/bcm2835-isp.rst
>
> diff --git a/Documentation/admin-guide/media/bcm2835-isp.rst b/Documentation/admin-guide/media/bcm2835-isp.rst
> new file mode 100644
> index 000000000000..e1c19f78435e
> --- /dev/null
> +++ b/Documentation/admin-guide/media/bcm2835-isp.rst
> @@ -0,0 +1,127 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +BCM2835 ISP Driver
> +==================
> +
> +Introduction
> +------------
> +
> +The BCM2835 Image Sensor Pipeline (ISP) is a fixed function hardware pipeline
> +for performing image processing operations. Images are fed to the input
> +of the ISP through memory frame buffers. These images may be in various YUV,
> +RGB, or Bayer formats.

Does the ISP really support RGB or YUV input images ? Is this supported
by the driver ?

> A typical use case would have Bayer images obtained from
> +an image sensor by the BCM2835 Unicam peripheral, written to a memory
> +frame buffer, and finally fed into the input of the ISP. Two concurrent output
> +images may be generated in YUV or RGB format at different resolutions.
> +Statistics output is also generated for Bayer input images.
> +
> +The bcm2835-isp driver exposes the following media pads as V4L2 device nodes:

This sounds weird. Pads are not video nodes, are they ? Or are those
MMAL pads ?

> +
> +.. tabularcolumns:: |l|l|l|l|
> +
> +.. cssclass: longtable
> +
> +.. flat-table::
> +
> + * - *Pad*
> + - *Direction*
> + - *Purpose*
> + - *Formats*
> +
> + * - "bcm2835-isp0-output0"
> + - sink
> + - Accepts Bayer, RGB or YUV format frame buffers as input to the ISP HW
> + pipeline.
> + - :ref:`RAW8 <V4L2-PIX-FMT-SRGGB8>`,
> + :ref:`RAW10P <V4L2-PIX-FMT-SRGGB10P>`,
> + :ref:`RAW12P <V4L2-PIX-FMT-SRGGB12P>`,
> + :ref:`RAW14P <V4L2-PIX-FMT-SRGGB14P>`,
> + :ref:`RAW16 <V4L2-PIX-FMT-SRGGB16>`,
> + :ref:`RGB24/BGR24 <V4L2-PIX-FMT-RGB24>`,
> + :ref:`YUYV <V4L2-PIX-FMT-YUYV>`,
> + :ref:`YVYU <V4L2-PIX-FMT-YVYU>`,
> + :ref:`UYVY <V4L2-PIX-FMT-UYVY>`,
> + :ref:`VYUY <V4L2-PIX-FMT-VYUY>`,
> + :ref:`YUV420/YVU420 <V4L2-PIX-FMT-YUV420>`
> +
> + * - "bcm2835-isp0-capture1"
> + - source
> + - High resolution YUV or RGB processed output from the ISP.
> + - :ref:`RGB565 <V4L2-PIX-FMT-RGB565>`,
> + :ref:`RGB24/BGR24 <V4L2-PIX-FMT-RGB24>`,
> + :ref:`ABGR32 <V4L2-PIX-FMT-ABGR32>`,
> + :ref:`YUYV <V4L2-PIX-FMT-YUYV>`,
> + :ref:`YVYU <V4L2-PIX-FMT-YVYU>`,
> + :ref:`UYVY <V4L2-PIX-FMT-UYVY>`,
> + :ref:`VYUY <V4L2-PIX-FMT-VYUY>`.
> + :ref:`YUV420/YVU420 <V4L2-PIX-FMT-YUV420>`,
> + :ref:`NV12/NV21 <V4L2-PIX-FMT-NV12>`,
> +
> + * - "bcm2835-isp0-capture2"
> + - source
> + - Low resolution YUV processed output from the ISP. The output of
> + this pad cannot have a resolution larger than the "bcm2835-isp0-capture1" pad in any dimension.
> + - :ref:`YUYV <V4L2-PIX-FMT-YUYV>`,
> + :ref:`YVYU <V4L2-PIX-FMT-YVYU>`,
> + :ref:`UYVY <V4L2-PIX-FMT-UYVY>`,
> + :ref:`VYUY <V4L2-PIX-FMT-VYUY>`.
> + :ref:`YUV420/YVU420 <V4L2-PIX-FMT-YUV420>`,
> + :ref:`NV12/NV21 <V4L2-PIX-FMT-NV12>`,
> +
> + * - "bcm2835-isp0-capture1"

Is that capture3 ?

Maybe the video nodes should be renamed to make their purpose clearer ?

> + - source
> + - Image statistics calculated from the input image provided on the
> + "bcm2835-isp0-output0" pad. Statistics are only available for Bayer
> + format input images.
> + - :ref:`v4l2-meta-fmt-bcm2835-isp-stats`.
> +
> +Pipeline Configuration
> +----------------------
> +
> +The ISP pipeline can be configure through user-space by calling
> +:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` on the “bcm2835-isp0-output0”
> +node with the appropriate parameters as shown in the table below.
> +
> +.. tabularcolumns:: |p{2cm}|p{5.0cm}|
> +
> +.. cssclass: longtable
> +
> +.. flat-table::
> +
> + * - *id*
> + - *Parameter*
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_CC_MATRIX``
> + - struct :c:type:`bcm2835_isp_custom_ccm`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_LENS_SHADING``
> + - struct :c:type:`bcm2835_isp_lens_shading`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_BLACK_LEVEL``
> + - struct :c:type:`bcm2835_isp_black_level`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_GEQ``
> + - struct :c:type:`bcm2835_isp_geq`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_GAMMA``
> + - struct :c:type:`bcm2835_isp_gamma`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_DENOISE``
> + - struct :c:type:`bcm2835_isp_denoise`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_SHARPEN``
> + - struct :c:type:`bcm2835_isp_sharpen`
> +
> + * - ``V4L2_CID_USER_BCM2835_ISP_DPC``
> + - struct :c:type:`bcm2835_isp_dpc`
> +
> +++++++++++++++++++++++++
> +Configuration Parameters
> +++++++++++++++++++++++++
> +
> +.. kernel-doc:: include/uapi/linux/bcm2835-isp.h
> + :functions: bcm2835_isp_rational bcm2835_isp_ccm bcm2835_isp_custom_ccm
> + bcm2835_isp_gain_format bcm2835_isp_lens_shading
> + bcm2835_isp_black_level bcm2835_isp_geq bcm2835_isp_gamma
> + bcm2835_isp_denoise bcm2835_isp_sharpen
> + bcm2835_isp_dpc_mode bcm2835_isp_dpc
> diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
> index 32f82aed47d9..34e0d7102ef0 100644
> --- a/Documentation/userspace-api/media/drivers/index.rst
> +++ b/Documentation/userspace-api/media/drivers/index.rst
> @@ -31,6 +31,7 @@ For more details see the file COPYING in the source distribution of Linux.
> :maxdepth: 5
> :numbered:
>
> + bcm2835-isp
> ccs
> cx2341x-uapi
> dw100

--
Regards,

Laurent Pinchart