linux-kernel - Re: [PATCH] Input: egalax_ts - do not release gpio if probe successful

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Date:   Mon, 16 Jan 2017 15:43:40 +0100
From:   Gary Bisson <gary.bisson@...ndarydevices.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Input: egalax_ts - do not release gpio if probe successful

Hi Dmitri,

On Fri, Jan 13, 2017 at 12:40 AM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Fri, Jan 13, 2017 at 12:03:43AM +0100, Gary Bisson wrote:
>> Hi Dmitri,
>>
>> On Thu, Jan 12, 2017 at 10:30:19AM -0800, Dmitry Torokhov wrote:
>> > Hi Gary,
>> >
>> > On Wed, Jan 11, 2017 at 06:28:41PM +0100, Gary Bisson wrote:
>> > > Thus preventing anyone to later modify the interrupt GPIO direction
>> > > and/or state without the driver knowing.
>> >
>> > I am afraid not releasing gpio after waking up the controller will cause
>> > request_irq to fail if we are using the same pin for interrupt and
>> > wakeup (as majority of current DTSes do: see
>> > arch/arm/boot/dts/imx53-tx53-x13x.dts for example).
>>
>> No, keeping the GPIO doesn't prevent from requesting the IRQ.
>>
>> However it keeps other drivers/users from changing the GPIO as output
>> later on.
>
>
> Hmm, I think _gpiod_direction_output_raw() will not let them as it
> checks FLAG_USED_AS_IRQ, so as long as it's the same line it's OK. But I
> guess if they are separate some other component might try to grab it and
> mess with it.
>
> OK, in this case please:
>
> - use devm_gpiod_get
> - request with GPIOD_OUT_LOW
> - do not override the return value with -ENODEV (especially important
>   with probe deferrals)
> - lose gpiod_direction_output() call
> - move everything into egalax_ts_probe() as egalax_wake_up_device() is
>   no longer self-contained.

Thanks for reviewing. I'll try to do the v2 this week.

Regards,
Gary