linux-kernel - Re: [PATCH] ACPI / GPIO: Pass index to acpi_get_gpiod_by

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Message-ID: <5459646E.9000707@linux.intel.com>
Date:	Tue, 04 Nov 2014 15:42:38 -0800
From:	Darren Hart <dvhart@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Grant Likely <grant.likely@...retlab.ca>
CC:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Alexandre Courbot <acourbot@...dia.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / GPIO: Pass index to acpi_get_gpiod_by_index()
 when using properties



On 11/4/14 14:54, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: ACPI / property: Drop size_prop from acpi_dev_get_property_reference()
> 
> The size_prop argument of the recently added function
> acpi_dev_get_property_reference() is not used by the only current
> caller of that function and is very unlikely to be used at any time
> going forward.
> 
> Namely, for a property whose value is a list of items each containing
> a references to a device object possibly accompanied by some integers,
> the number of items in the list can always be computed as the number
> of elements of type ACPI_TYPE_LOCAL_REFERENCE in the property package.
> Thus it should never be necessary to provide an additional "cells"
> property with a value equal to the number of items in that list.

In this case, do we never expect a property to contain more than one
ACPI_TYPE_LOCAL_REFERENCE?

Package () { "foobar",
              Package () {
                  "PCI0.FOO", "PCI0.BAR", 0, 1, 0,
                  "PCI0.FOO", "PCI0.BAR2", 0, 1, 1
              }
}

This seems like it could be useful for connecting various types of
devices together, but I confess not to have a specific exmaple in mind.
It does concern me to limit the data format in this way.

I suppose should such a case become necessary, we can deal with the
issue then - and still avoid having a potential abuse point in the API
from the start.

-- 
Darren Hart
Intel Open Source Technology Center
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