Re: [PATCH 1/4] gpiolib: add support for bias pull disable

Nuno Sá
2022-07-14T15:46:51Z

On Thu, 2022-07-14 at 18:08 +0300, Andy Shevchenko wrote:
> On Thu, Jul 14, 2022 at 03:02:08PM +0200, Nuno Sá wrote:
> > On Thu, 2022-07-14 at 20:00 +0800, Kent Gibson wrote:
> > > On Thu, Jul 14, 2022 at 10:47:27AM +0200, Nuno Sá wrote:
>
> ...
>
> > > If that solves your immediate problem then you need to decide
> > > what
> > > problem your patch is trying to address.
> >
> > So my patch is trying to solve exactly this case because (IMO), it
> > does
> > not make sense for consumers drivers to have to do the above code.
> > Moreover, they would need some custom firmware property (eg:
> > devicetree) for the cases where we want to disable BIAS since we
> > cannot
> > just assume we want to do it.
>
> Why? This is the main question. Why do you need that _in kernel_ API.
>
> > Well, maybe we can just assume FLAG_BIAS_DISABLE in gpiolib (when
> > trying to get the gpiod) if no PULL is specified. However, I do
> > have
> > some concerns with it (see my conversation with Andy in the cover).
>
> It's AS IS if you trust firmware.
>

In my use case, there's no firmware controlling the pin... The input
driver (which exposes the gpichip) directly controls the pins and I
want to have a way to tell it (from firmware) to disable the BIAS if
users want to do so (by default it's pull-up)...

- Nuno Sá