linux-kernel - Re: [PATCH 3/3] gpio: Add reference counting for non-exclusive GPIOs

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Message-ID: <20181126143028.GO16508@imbe.wolfsonmicro.main>
Date:   Mon, 26 Nov 2018 14:30:28 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Mark Brown <broonie@...nel.org>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>
Subject: Re: [PATCH 3/3] gpio: Add reference counting for non-exclusive GPIOs

On Mon, Nov 26, 2018 at 02:09:27PM +0000, Mark Brown wrote:
> On Mon, Nov 26, 2018 at 01:00:01PM +0000, Charles Keepax wrote:
> > On Fri, Nov 23, 2018 at 01:25:22PM +0000, Mark Brown wrote:
> 
> > > help the multiple users find each other somehow.  I think what we want
> > > to do here is either push the gpiod requests into the regulator core or
> > > change things so that once the regulator is registered with the
> > > regulator core the regulator core owns and is responsible for freeing
> > > the regulator.
> 
> > On the co-ordinating do we expect that the behaviour will
> > be that the GPIO should in the "enabled" state whenever any
> > regulator is requesting it? IE. the GPIO state is an OR of
> > the regulator states. Or are we expecting to handle more
> > complex interaction?
> 
> For the regulators that's what we do, yes - it's like they're all
> sharing a single regulator.  That probably won't be true in general for
> all GPIO users.

Would there perhaps be milage in looking at just making
the regulator core request the GPIO, rather than the end
drivers? Gives us a single request/free point. We don't need
any special flags in the GPIO layer, as its just a single
user as far as GPIO is concerned.

Thanks,
Charles