linux-kernel - Re: [PATCH v3] gpio: lib-sysfs: Add 'wakeup' attribute

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Date:	Fri, 31 Oct 2014 09:16:58 -0700
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	<linux-api@...r.kernel.org>, Alexandre Courbot <gnurou@...il.com>,
	Jonathan Corbet <corbet@....net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v3] gpio: lib-sysfs: Add 'wakeup' attribute

On Fri, 2014-10-31 at 08:03AM +0100, Linus Walleij wrote:
> On Mon, Oct 27, 2014 at 7:30 PM, Soren Brinkmann
> <soren.brinkmann@...inx.com> wrote:
> 
> > Add an attribute 'wakeup' to the GPIO sysfs interface which allows
> > marking/unmarking a GPIO as wake IRQ.
> > The file 'wakeup' is created in each exported GPIOs directory, if an IRQ
> > is associated with that GPIO and the irqchip implements set_wake().
> > Writing 'enabled' to that file will enable wake for that GPIO, while
> > writing 'disabled' will disable wake.
> > Reading that file will return either 'disabled' or 'enabled' depening on
> > the currently set flag for the GPIO's IRQ.
> >
> > Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
> > Reviewed-by: Alexandre Courbot <acourbot@...dia.com>
> > ---
> > v3:
> >  - add documentation
> > v2:
> >  - fix error path to unlock mutex before return
> (...)
> 
> Looking better!
> 
> > +       "wakeup" ... reads as either "enabled" or "disabled". Write these
> > +               strings to set/clear the 'wakeup' flag of the IRQ associated
> > +               with this GPIO. If the IRQ has the 'wakeup' flag set, it can
> > +               wake the system from sleep states.
> > +
> > +               This file exists only if the pin can generate interrupts and
> > +               the driver implements the required infrastructure.
> 
> Should this not be 0/1 rather than the string "enabled"/"disabled"?
> 
> I think that is the common pattern in sysfs?
> 
> Not sure, but want an indication from the ABI people.

So, as I told Alexandre, 'wakeup' including the values 'enabled' &
'disabled' is how devices that support wake expose this functionality. I
think this is more in line with what already exists. As reference, have
a look at https://www.kernel.org/doc/Documentation/power/devices.txt. It
has a section '/sys/devices/.../power/wakeup files'.

	Thanks,
	Sören
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