linux-kernel - Re: [PATCH v2] regulator: arizona-ldo1: Use correct device to get enable GPIO

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Date:   Wed, 20 Jun 2018 09:14:42 +0100
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Mark Brown <broonie@...nel.org>, <hias@...us.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        <patches@...nsource.cirrus.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] regulator: arizona-ldo1: Use correct device to get
 enable GPIO

On Tue, Jun 19, 2018 at 11:46:36PM +0300, Andy Shevchenko wrote:
> On Tue, Jun 19, 2018 at 6:10 PM, Charles Keepax
> <ckeepax@...nsource.cirrus.com> wrote:
> > Currently the enable GPIO is being looked up on the regulator
> > device itself but that does not have its own DT node, this causes
> > the lookup to fail and the regulator not to get its GPIO. The DT
> > node is shared across the whole MFD and as such the lookup needs
> > to happen on that parent device.
> 
> > Moving the lookup to the parent
> > device also means devres can no longer be used as the life time
> > would attach to the wrong device.
> 
> This part I didn't get.
> Why we can't use devm_...(parent_dev, ...) instead?
> 

Because it is possible to unbind the regulator driver itself,
which would leave the GPIO as acquired, since the MFD is never
unbound. Then when you rebind the regulator the GPIO would
already be held by the previous instantiation of the regulator
driver.

Thanks,
Charles