linux-kernel - Re: [PATCH] regulator: core: Add devres versions of regulator

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Date:   Sat, 10 Aug 2019 09:44:45 +0800
From:   Chuhong Yuan <hslester96@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] regulator: core: Add devres versions of regulator_enable/disable

On Fri, Aug 9, 2019 at 11:11 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Fri, Aug 09, 2019 at 11:03:52AM +0800, Chuhong Yuan wrote:
> > I wrote a coccinelle script to detect possible chances
> > of utilizing devm_() APIs to simplify the driver.
> > The script found 147 drivers in total and 22 of them
> > have be patched.
>
> > Within the 125 left ones, at least 31 of them (24.8%)
> > are hindered from benefiting from devm_() APIs because
> > of lack of a devres version of regulator_enable().
>
> I'm not super keen on managed versions of these functions since they're
> very likely to cause reference counting issues between the probe/remove
> path and the suspend/resume path which aren't obvious from the code, I'm
> especially worried about double frees on release.

I find that 29 of 31 cases I found call regulator_disable() only when encounter
probe failure or in .remove.
So I think the devm versions of regulator_enable/disable() will not cause big
problems.

I even found a driver to forget to disable regulator when encounter
probe failure,
which is drivers/iio/adc/ti-adc128s052.c.
And a devm version of regulator_enable() can prevent such mistakes.