Re: [PATCH 1/1] v4l: Add camera voice coil lens control class, current control

From: Laurent Pinchart
Date: Fri Jun 17 2016 - 18:39:52 EST


On Saturday 18 Jun 2016 00:11:49 Pavel Machek wrote:
> Hi!
> >> I also don't think the FOCUS_ABSOLUTE controls is a really good one for
> >> the voice coil lens current. I expect more voice coil lens controls
> >> (linear vs. PWM mode, ringing compensation...) to be needed so I think
> >> it's worth a new class.
> Well, I do agree that that the new class is fine (and have no problem
> with your proposal), but I'd like to understand why FOCUS_ABSOLUTE is
> unsuitable. I'm actually thinking about writing very simple userspace
> camera, without autofocus, where user would just select
> "infinity"/"1m"/"50cm" ... and for that FOCUS_ABSOLUTE is equivalent
> > Right, I still think movement mode should be standard control :)
> What options would you like to see for movement mode?

I've discussed this with Sakari offline a few days ago. I won't nack this
patch, but to ack it I'd like to have a better understanding of the big
picture when it comes to focus and lens control. The proposed new control can
make sense when taken in isolation, but I can't tell whether it still would
when associated with the other controls that would be needed to properly
control a voice coil lens.

If someone has analyzed the existing voice coil lens controllers and could
share the result, in term of what parameters need to be controlled by the
system and how they should be controlled, that would be very appreciated. Even
better would be a real userspace implementation of a voice coil lens control


Laurent Pinchart