e3185e1d7c
Some Allwinner platforms come with an Image Signal Processor, which supports various features in order to enhance and transform data received by image sensors into good-looking pictures. In most cases, the data is raw bayer, which gets internally converted to RGB and finally YUV, which is what the hardware produces. This driver supports ISPs that are similar to the A31 ISP, which was the first standalone ISP found in Allwinner platforms. Simpler ISP blocks were found in the A10 and A20, where they are tied to a CSI controller. Newer generations of Allwinner SoCs (starting with the H6, H616, etc) come with a new camera subsystem and revised ISP. Even though these previous and next-generation ISPs are somewhat similar to the A31 ISP, they have enough significant differences to be out of the scope of this driver. While the ISP supports many features, including 3A and many enhancement blocks, this implementation is limited to the following: - V3s (V3/S3) platform support; - Bayer media bus formats as input; - Semi-planar YUV (NV12/NV21) as output; - Debayering with per-component gain and offset configuration; - 2D noise filtering with configurable coefficients. Since many features are missing from the associated uAPI, the driver is aimed to integrate staging until all features are properly described. On the technical side, it uses the v4l2 and media controller APIs, with a video node for capture, a processor subdev and a video node for parameters submission. A specific uAPI structure and associated v4l2 meta format are used to configure parameters of the supported modules. One particular thing about the hardware is that configuration for module registers needs to be stored in a DMA buffer and gets copied to actual registers by the hardware at the next vsync, when instructed by a flag. This is handled by the "state" mechanism in the driver. Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.