On Wednesday 01 October 2014 04:11:20 Rafael J. Wysocki wrote:

From: Mika Westerberg <mika.westerberg@linux.intel.com>

This document describes the data format and interfaces of ACPI device
specific properties.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Darren Hart <redacted>
Signed-off-by: Rafael J. Wysocki <redacted>

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