From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v3 04/15] ACPI: Document ACPI device specific properties Date: Wed, 01 Oct 2014 09:59:14 +0200 Message-ID: <1979325.jM0BQzDCTX@wuerfel> References: <1410868367-11056-1-git-send-email-mika.westerberg@linux.intel.com> <1852462.V1jlbi8OPt@vostro.rjw.lan> <5597683.oi0VxOogFu@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: Received: from mout.kundenserver.de ([212.227.126.131]:50039 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750850AbaJAH7Z (ORCPT ); Wed, 1 Oct 2014 03:59:25 -0400 In-Reply-To: <5597683.oi0VxOogFu@vostro.rjw.lan> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" Cc: linux-kernel@vger.kernel.org, Mika Westerberg , linux-acpi@vger.kernel.org, devicetree@vger.kernel.org, Greg Kroah-Hartman , Linus Walleij , Alexandre Courbot , Dmitry Torokhov , Bryan Wu , Lee Jones , Grant Likely , Aaron Lu , Darren Hart On Wednesday 01 October 2014 04:11:20 Rafael J. Wysocki wrote: > From: Mika Westerberg > > This document describes the data format and interfaces of ACPI device > specific properties. > > Signed-off-by: Mika Westerberg > Signed-off-by: Darren Hart > Signed-off-by: Rafael J. Wysocki Overall looks sane, but I wonder if we should try harder to not duplicate some of the mistakes we made in the DT bindings. Two points in particular stick out: > +2.3 Strings > +----------- > +String properties can be used to describe many things like labels for GPIO > +buttons, compability ids, etc. > + > +A string property looks like this: > + > + Package () {"pwm-names", "backlight"}, The way we name things in DT using separate "foos" and "foo-names" properties is a bit quirky. Those are always defined on a per-subsystem level, not a per-device level though, so it should be possible to come up with a better representation in ACPI. Since the device driver should never look into the "foo-names" property itself but just pass down the name into the subsystem, the "foo" subsystem could instead have a way to add an (optional) name for each reference. This is something the DT syntax doesn't allow because you can't have both a phandle and a string in a single property but I think the ACPI packages can do it, and it wouldn't change the basic structure. > +The referenced ACPI device is returned in args->adev if found. > + > +In addition to simple object references it is also possible to have object > +references with arguments. These are represented in ASL as follows: > + > + Device (\_SB.PCI0.PWM) > + { > + Name (_DSD, Package () { > + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), > + Package () { > + Package () {"#pwm-cells", 2} > + } > + }) > + } > + Similarly, the "#foo-cells" syntax is an artifact of the limitations of the DT syntax, and I'd assume there would be a better way to encode this in ACPI. Also, a "cell" in Open Firmware is defined as a big-endian 32-bit value, which doesn't directly correspond to something in ACPI, and the '#' character is an artifact of the use of the Forth language in Open Firmware, which you also don't have here. Arnd