linux-kernel - Re: [PATCH] IIO: Adds ACPI support for ST gyroscopes

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Message-ID: <20150325094327.GW1878@lahna.fi.intel.com>
Date:	Wed, 25 Mar 2015 11:43:27 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Lars-Peter Clausen <lars@...afoo.de>,
	Robert Dolca <robert.dolca@...il.com>,
	Robert Dolca <robert.dolca@...el.com>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	Jonathan Cameron <jic23@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Denis CIOCCA <denis.ciocca@...com>
Subject: Re: [PATCH] IIO: Adds ACPI support for ST gyroscopes

On Wed, Mar 25, 2015 at 09:44:34AM +0100, Linus Walleij wrote:
> On Tue, Mar 24, 2015 at 4:06 PM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
> 
> > This has few problems that I have not yet figured out. Maybe someone
> > here can suggest what to do:
> >
> >  1) Who is responsible in releasing the GPIO?
> >  2) What if the driver wants to use that pin as a GPIO instead? The GPIO
> >     is already requested by the I2C core.
> 
> In the DT usecase we actually specify that in the DTS file
> so we don't have the problem. Either the consumer accesses
> the irqchip API with:
> 
> interrupts = <nn nn>;
> 
> or it accesses the GPIO API with:
> 
> gpios = <nn nn>;

OK, I see.

> so in that sense it is clear what is requested. Then the core
> of course uses gpiochip_lock/unlock_as_irq() to handle the
> case where bugs make a collision (like if both were specified
> and both APIs tries to access the same resource).

Where in the core code gpiochip_lock/unlock_as_irq() is called for
these? At least of_irq_get() doesn't seem to be doing that. Maybe I'm
looking at the wrong place.

> But as long as the DTS file is consistent there is no problem.
> 
> So it seems the ACPI tables are lacking this semantic
> information?

I think the GpioIo/GpioInt separation serves the same purpose. Of course
both refer to GPIO controller instead of interrupt controller.
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