Re: [Ksummit-discuss] [TECH TOPIC] Sensors and similar - subsystem interactions, divisions, bindings etc.

[Mauro Carvalho Chehab <mchehab@infradead.org>]

Em Wed, 20 Jul 2016 22:18:11 +0100
Jonathan Cameron <jic23@kernel.org> escreveu:

> Hi All,
> 
> This topic would be around the way the various subsystems interact, in the
> rough area of 'sensors' (I haven't yet had much of an issue with subsystem
> crossing with output devices but maybe that's just over the next hill!)

Yeah, there is a gray area here as devices become more complex.
So, I'm interested on such topic.

> Scope may well be wider but includes:
> * input (some of it)
> * hwmon
> * iio
> * comedi(?)
> * thermal
> * power/battery
> * gpio - the blur between gpios and beaglescope / PLC type I/O.
> * v4l - when does a device jump from being a multi pixel thermopile
> to a thermal camera? Smart fingerprint scanners etc.  Gesture recognition
> sensors (effectively 9ish pixel cameras)

For devices that provide images somehow, I'd say that the best would be
to implement them as via the V4L2 API. We'll likely need to discuss it
case by case, specially for early cross-subsystem drivers, though, as
it is not trivial to identify the subsystem boundaries, and sometimes
multiple APIs from different subsystems is needed. Also, it is not
clear where such drivers would fit at the Kernel tree.

One interesting case is an input device driver with multi-finger
support (drivers/input/touchscreen/sur40.c). I suspect we'll have
more cases like that over time.

> * Lots of random things we haven't seen yet.

Thanks,
Mauro