Re: [PATCH v3 2/4] media: i2c: Add ST VD55G0 global shutter sensor driver

[Sergey Lebedev <lsa.uz@pm.me>]

Hi Benjamin,

On Tue, Nov 10, 2026 at 10:46:57AM +0100, Benjamin Mugnier wrote:
> From a user perspective they are mostly interchangeable. vd55g1 uses
> AE_TARGET_PERCENTAGE while vd56g3 uses AE_COMPENSATION for instance.
>
> The downstream driver uses AE_TARGET_PERCENTAGE and that's why you have
> it here. It would make more sense to use AE_COMPENSATION semantic wise,
> but this is not a deal breaker.

I tried AE_COMPENSATION on the VD55G0 here, with the firmware patch the
driver loads. Positive values work as UM2829 says, but a negative one
drives the AE to its maximum.

A white sheet in front of the camera, the illuminator on, each value in
a stream of its own:
- AE_TARGET_PERCENTAGE 7, 14, 27: exposure 27, 49, 89 lines;
- target 7 with +1 EV (0x0100) and +2 EV (0x0200): 48 and 91 lines;
- target 14 with -1 EV (0xff00): 1796 lines, analogue gain 24, digital
  gain 2048.

On the Dgrey test pattern every negative value did the same: -0.5, -1
and -2 EV in two's complement, and -1 and -2 EV as sign and magnitude
(0x8100, 0x8200). AE_TARGET_PERCENTAGE works both ways, so v4 keeps it.

Is this known for the VD55G0 firmware?

Sergey