media: uapi: Add meta pixel format for PiSP BE config

Add format description for the PiSP Back End configuration parameter
buffer.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

2 files changed, 57 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/v4l/meta-formats.rst b/Documentation/userspace-api/media/v4l/meta-formats.rst
index c23aac823d2c..c6e56b5888bc 100644
--- a/Documentation/userspace-api/media/v4l/meta-formats.rst
+++ b/Documentation/userspace-api/media/v4l/meta-formats.rst
@@ -15,6 +15,7 @@ These formats are used for the :ref:`metadata` interface only.
     metafmt-d4xx
     metafmt-generic
     metafmt-intel-ipu3
+    metafmt-pisp-be
     metafmt-rkisp1
     metafmt-uvc
     metafmt-vivid
diff --git a/Documentation/userspace-api/media/v4l/metafmt-pisp-be.rst b/Documentation/userspace-api/media/v4l/metafmt-pisp-be.rst
new file mode 100644
index 000000000000..3281fe366c86
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/metafmt-pisp-be.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. _v4l2-meta-fmt-rpi-be-cfg:
+
+************************
+V4L2_META_FMT_RPI_BE_CFG
+************************
+
+Raspberry Pi PiSP Back End configuration format
+===============================================
+
+The Raspberry Pi PiSP Back End memory-to-memory image signal processor is
+configured by userspace by providing a buffer of configuration parameters
+to the `pispbe-config` output video device node using the
+:c:type:`v4l2_meta_format` interface.
+
+The PiSP Back End processes images in tiles, and its configuration requires
+specifying two different sets of parameters by populating the members of
+:c:type:`pisp_be_tiles_config` defined in the ``pisp_be_config.h`` header file.
+
+The `Raspberry Pi PiSP technical specification
+<https://datasheets.raspberrypi.com/camera/raspberry-pi-image-signal-processor-specification.pdf>`_
+provide detailed description of the ISP back end configuration and programming
+model.
+
+Global configuration data
+-------------------------
+
+The global configuration data describe how the pixels in a particular image are
+to be processed and is therefore shared across all the tiles of the image. So
+for example, LSC (Lens Shading Correction) or Denoise parameters would be common
+across all tiles from the same frame.
+
+Global configuration data are passed to the ISP by populating the member of
+:c:type:`pisp_be_config`.
+
+Tile parameters
+---------------
+
+As the ISP processes images in tiles, each set of tiles parameters describe how
+a single tile in an image is going to be processed. A single set of tile
+parameters consist of 160 bytes of data and to process a batch of tiles several
+sets of tiles parameters are required.
+
+Tiles parameters are passed to the ISP by populating the member of
+``pisp_tile`` and the ``num_tiles`` fields of :c:type:`pisp_be_tiles_config`.
+
+Raspberry Pi PiSP Back End uAPI data types
+==========================================
+
+This section describes the data types exposed to userspace by the Raspberry Pi
+PiSP Back End. The section is informative only, for a detailed description of
+each field refer to the `Raspberry Pi PiSP technical specification
+<https://datasheets.raspberrypi.com/camera/raspberry-pi-image-signal-processor-specification.pdf>`_.
+
+.. kernel-doc:: include/uapi/linux/media/raspberrypi/pisp_be_config.h