ISP on imx8mp with libcamera: how is the sensor involved?

[Martin Kepplinger]

hi Laurent, Jacobo and all,

I'm planning to test libcamera on imx8mp (latest mainline v6.12-based
kernel without any nxp-stuff, where ISI works fine) when changing the
dts to cam->mipi->ISP and I have one high-level conceptual question:

I short: How is or can the sensor itself be involved during the running
IPA?

Simplified: When the libcamera ISP algorithm would result in, say,
"gain too low, let's increase", shouldn't it do that at the sensor
itself? (Let's say it's a "stupid" sensor hardware module that can only
set absolte values, without an ISP on it).

The above is at least not what I find when reading libcamera docs. It
looks like the IPA is indeed restricted to ISP-settings and never
changes sensor-controls...

When looking at what NXP intends to do with their kernels, they require
to patch the sensor kernel drivers to support an ISP-API so that the
sensor itself is involved... (of course require lots of other libraries
and whatnot that I hope to be able to avoid using).

Do you know what I mean and can you point me in the right direction?

thank you!

                            martin