linux-kernel - Re: [PATCH v3 10/15] leds: leds-gpio: Add ACPI probing support

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Message-ID: <2433277.SBXQyCNNAQ@wuerfel>
Date:	Thu, 02 Oct 2014 12:44:11 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	devicetree@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Aaron Lu <aaron.lu@...el.com>,
	Darren Hart <dvhart@...ux.intel.com>
Subject: Re: [PATCH v3 10/15] leds: leds-gpio: Add ACPI probing support

On Thursday 02 October 2014 12:55:36 Mika Westerberg wrote:
> On Wed, Oct 01, 2014 at 04:14:20PM +0200, Arnd Bergmann wrote:
> > On Wednesday 01 October 2014 17:04:41 Mika Westerberg wrote:
> > > 
> > > > On the question what to put into the name and type fields, that is
> > > > unrelated. The type is supposed to be for the 'device_type' property
> > > > in DT, which we should never rely on in a driver that supports both
> > > > APCI and DT. In Linux we only use that for "pci", "cpu" and "memory",
> > > > all of which have their own way of getting probed in ACPI.
> > > > The "name" is normally ignored in DT as well, except for backwards
> > > > compatibility with old bindings, but I would argue that you should not
> > > > just put "prp0001" in there. Either leave it empty like type, or use
> > > > the name of the device as it appears in the ACPI tables, such as "DEV0"
> > > > or "PWM".
> > > 
> > > OK, I think it makes sense to leave them empty. I remember I tried that
> > > at some point but it didn't work without N and T fields. Is there some
> > > example what to put there in case of empty?
> > > 
> > > Something like "of:N*T*Cgpio-leds" perhaps?
> > 
> > Sorry, don't know. If I read the code right, the type field in DT ends
> > up being "<NULL>" for any device that doesn't set the device_type 
> > property, but that seems a bit silly and probably isn't worth copying.
> 
> OK, I checked and udev wants to have both N and T but they can be left
> empty. If there are no objections the modalias will look like this:
> 
> [root@...01 ~]# cat /sys/bus/spi/devices/spi-PRP0001\:00/modalias 
> of:Nat25TCatmel,at25
> 
> In other words name is the ACPI device name (AT25) in lower case, T is
> left empty and C is the compatible property.

Yes, seems ok to me.

	Arnd
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