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>

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

Documentation/userspace-api/media/v4l/metafmt-pisp-be.rst

+.. 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

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -1465,6 +1465,7 @@ 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_RPI_BE_CFG:	descr = "RPi PiSP BE Config format"; 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;

include/uapi/linux/videodev2.h

@@ -843,6 +843,9 @@ 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 */
 
+/* Vendor specific - used for RaspberryPi PiSP */
+#define V4L2_META_FMT_RPI_BE_CFG	v4l2_fourcc('R', 'P', 'B', 'C') /* PiSP BE configuration */
+
 #ifdef __KERNEL__
 /*
  * Line-based metadata formats. Remember to update v4l_fill_fmtdesc() when