Hi,

On Mon 13 Sep 21, 10:31, Maxime Ripard wrote:

On Fri, Sep 10, 2021 at 08:41:45PM +0200, Paul Kocialkowski wrote:

quoted

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.

We can add new features/interfaces to a !staging driver. Why do you
think staging is required?

This is true for the driver but not so much for the uAPI, so it seems that
the uAPI must be added to staging in some way. Then I'm not sure it makes sense
to have a !staging driver that depends on a staging uAPI.

Besides that, I added it to staging because that's the process that was
followed by rkisp1, which is a very similar case.

quoted

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.

This meta format needs to be documented

You're right, there should probably be a pixfmt-meta-sun6i-isp.rst
documentation file. I guess it should live along in the staging driver
directory for now and be destaged later.

Cheers,

Paul

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com