Re: [RFC] Addition of kernel

[Martyn Welch <martyn.welch@xxxxxxxxxxxxx>]

On Mon, 2019-06-17 at 14:39 +0200, Enrico Weigelt, metux IT consult
wrote:
> On 17.06.19 10:29, Martyn Welch wrote:
> We are currently in the position that we would like to pre-
> > configure
> > some GPIOs at boot time and be able to later affect the state of
> > GPIOs
> > configured as outputs or read the state of GPIOs previously
> > configured
> > as inputs.
> 
> what's the actual use case you've got in mind ?
> 
> I've got the feeling that these lines aren't really so "generic" in
> your case, but attached to something that has a particular meaning.
> 
> So, maybe something that deserves it's own driver ?
> 

You're right, the lines we wish to use this with aren't generic gpios,
they are primarily control lines for specific peripherals on the
device. I believe you are right, in an ideal world we could write
drivers for some of the functionality currently being exposed to user
space. But I'm fairly sure some of the lines don't have a sensible
driver model in which to fit them, specifically I can think of the
reset, boot mode control and interrupt lines for the GPS unit embedded
in the device I'm working on.

We are also not in the position to make major changes to how
functionality on this device has already been implemented and whilst we
are hoping to move to using proper drivers in some places, this is not
going to be tenable in all cases and we would ideally like to avoid
utilising a home grown (and certainly unlikely to be upstreamable)
solution for exposing these GPIOs.

Martyn