linux-kernel - Re: [PATCH v2 3/5] extcon: arizona: Convert to gpiod

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Message-ID: <20150619091349.GU32730@opensource.wolfsonmicro.com>
Date:	Fri, 19 Jun 2015 10:13:49 +0100
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	cw00.choi@...sung.com
Cc:	Lee Jones <lee.jones@...aro.org>,
	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	devicetree <devicetree@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	patches@...nsource.wolfsonmicro.com
Subject: Re: [PATCH v2 3/5] extcon: arizona: Convert to gpiod

On Fri, Jun 19, 2015 at 05:39:22PM +0900, Chanwoo Choi wrote:
> On Fri, Jun 19, 2015 at 5:14 PM, Charles Keepax
> <ckeepax@...nsource.wolfsonmicro.com> wrote:
> > On Fri, Jun 19, 2015 at 11:36:47AM +0900, Chanwoo Choi wrote:
> >> Hi Charles,
> >>
> >> On Thu, Jun 18, 2015 at 11:43 PM, Charles Keepax
> >> <ckeepax@...nsource.wolfsonmicro.com> wrote:
> >> > Convert to using the newer gpiod interface for the micd_pol_gpio.
> >> > Although we still carry support for the old gpio interface from pdata.
> >> >
> >> > Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> >> > ---
> >> > +                       mode = GPIOD_OUT_HIGH;
> >> > +               else
> >> > +                       mode = GPIOD_OUT_LOW;
> >> > +
> >> > +               info->micd_pol_gpio = gpiod_get_optional(arizona->dev,
> >> > +                                                        "wlf,micd-pol",
> >> > +                                                        GPIOD_OUT_LOW);
> >>
> >> You can use the devm_gpiod_get_optional() to manage the system
> >> resource automatically.
> >>
> >
> > We can't actually use the devm call here, we need to pass
> > arizona->dev as that is where the DT will reside, which is the
> > device for the MFD. But if the devm is attached to the device for
> > the MFD then it will not clear up when the extcon driver is
> > unloaded. As such we have to do the put manually.
> >
> > I will look at respinning for the other comments.
> 
> I don't understand. extcon-arizona.c used already following devm_* functions:
> - devm_kzalloc()
> - devm_regulator_get()
> - devm_extcon_dev_*()
> - devm_input_allocate_device()
> - devm_gpio_request_one()

Yes but if you look at those all of those are against &pdev->dev
which is the extcon device.

The gpiod interface expects the device passed to both contain
the of_node and be used for the devm operations. But we need to
use the extcon device for the devm operations, but the of_node is
contained on the MFD device.

So if I do:

devm_gpiod_get_optional(arizona->dev, ....

Then the gpiod won't be released when the extcon device is
removed. But if I do:

devm_gpiod_get_optional(&pdev->dev, ....

Then it won't be able to find the DT entries.

Thanks,
Charles
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