[libcamera-devel] [PATCH 0/2] Raspberry Pi: handle sensors more flexibly

[David Plowman]

Hi everyone

Here are a couple more patches aimed at allowing us to deal more
flexibly with "interesting" sensors.

The first patch simply makes the CamHelper's exposure-related methods
virtual. This gives greater flexibility on how we deal with sensors
where different modes have different signal levels. Differences
between modes can be accounted for with the gain methods (already
virtual), in the exposure (with this change), or via a combination of
the two.

Note that another solution to this involves fiddling around with the
AGC. It would have to know that modes can have different "base signal
levels", and account for the difference. I'm still in several minds
about whether I want to do this, so this change gives us options in
the meantime, and doesn't preclude messing with the AGC later if we
wish.

The second commit takes the view that if sensors seem to be asking for
the red/blue colour gains, then we should tell them. I guess there's a
risk that some sensors might seem to want these numbers, but we find
that we don't want to tell them. If that happens maybe the CamHelper
would have to tell us what to do, but this approach seems reasonable
to me at this point.

I also apply a fixed 256x multiplier to the colour gains before
passing them to the control. I don't think V4L2 docs mandate any
particular scale here? Maybe there's an argument for another
CamHelper function "ColourGainCode", or something like that.

Thoughts and suggestions welcome as always. Thanks!

David

David Plowman (2):
  ipa: raspberrypi: Make CamHelper exposure methods virtual
  ipa: raspberrypi: Update sensor's RED/BLUE balance controls when
    present

 src/ipa/raspberrypi/cam_helper.hpp              |  4 ++--
 src/ipa/raspberrypi/raspberrypi.cpp             | 17 ++++++++++++++---
 .../pipeline/raspberrypi/raspberrypi.cpp        |  9 +++++++++
 3 files changed, 25 insertions(+), 5 deletions(-)

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2.20.1