linux-kernel - Re: [PATCH 06/13] gpio / ACPI: Add support for

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Date:	Wed, 15 Oct 2014 11:46:20 +0300
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Grant Likely <grant.likely@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Aaron Lu <aaron.lu@...el.com>, devicetree@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>, Arnd Bergmann <arnd@...db.de>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 06/13] gpio / ACPI: Add support for _DSD device properties

On Tue, Oct 14, 2014 at 03:44:03PM +0200, Grant Likely wrote:
> On Tue, 07 Oct 2014 02:15:18 +0200
> , "Rafael J. Wysocki" <rjw@...ysocki.net>
>  wrote:
> > From: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > 
> > With release of ACPI 5.1 and _DSD method we can finally name GPIOs (and
> > other things as well) returned by _CRS. Previously we were only able to
> > use integer index to find the corresponding GPIO, which is pretty error
> > prone if the order changes.
> > 
> > With _DSD we can now query GPIOs using name instead of an integer index,
> > like the below example shows:
> > 
> >   // Bluetooth device with reset and shutdown GPIOs
> >   Device (BTH)
> >   {
> >       Name (_HID, ...)
> > 
> >       Name (_CRS, ResourceTemplate ()
> >       {
> >           GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
> >                   "\\_SB.GPO0", 0, ResourceConsumer) {15}
> >           GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
> >                   "\\_SB.GPO0", 0, ResourceConsumer) {27, 31}
> >       })
> > 
> >       Name (_DSD, Package ()
> >       {
> >           ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> >           Package ()
> > 	  {
> >               Package () {"reset-gpio", Package() {^BTH, 1, 1, 0 }},
> >               Package () {"shutdown-gpio", Package() {^BTH, 0, 0, 0 }},
> >           }
> >       })
> >   }
> > 
> > The format of the supported GPIO property is:
> > 
> >   Package () { "name", Package () { ref, index, pin, active_low }}
> > 
> >   ref - The device that has _CRS containing GpioIo()/GpioInt() resources,
> >         typically this is the device itself (BTH in our case).
> >   index - Index of the GpioIo()/GpioInt() resource in _CRS starting from zero.
> >   pin - Pin in the GpioIo()/GpioInt() resource. Typically this is zero.
> >   active_low - If 1 the GPIO is marked as active_low.
> > 
> > Since ACPI GpioIo() resource does not have field saying whether it is
> > active low or high, the "active_low" argument can be used here. Setting
> > it to 1 marks the GPIO as active low.
> > 
> > In our Bluetooth example the "reset-gpio" refers to the second GpioIo()
> > resource, second pin in that resource with the GPIO number of 31.
> > 
> > This patch implements necessary support to gpiolib for extracting GPIOs
> > using _DSD device properties.
> 
> Patch looks good, but please put the above description into
> /Documentation until we've got a better place to document extra bindings.

Thanks for the review.

If you don't mind, I would like to make a separate patch on top of this
series adding this description to Documentation/acpi/properties.txt.
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