On Tue, 07 Oct 2014 02:14:06 +0200 , "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> wrote: > From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > > This document describes the data format and interfaces of ACPI device > specific properties. > > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > Signed-off-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > --- > Documentation/acpi/properties.txt | 376 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 376 insertions(+) > create mode 100644 Documentation/acpi/properties.txt > > Index: linux-pm/Documentation/acpi/properties.txt > =================================================================== > --- /dev/null > +++ linux-pm/Documentation/acpi/properties.txt > @@ -0,0 +1,376 @@ > +ACPI device properties > +====================== > +This document describes the format and interfaces of ACPI device > +properties as specified in "Device Properties UUID For _DSD" available > +here: > + > +http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf > + > +1. Introduction > +--------------- > +In systems that use ACPI and want to take advantage of device specific > +properties, there needs to be a standard way to return and extract > +name-value pairs for a given ACPI device. > + > +An ACPI device that wants to export its properties must implement a > +static name called _DSD that takes no arguments and returns a package of > +packages: > + > + Name (_DSD, Package () { > + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), > + Package () { > + Package () {"name1", <VALUE1>}, > + Package () {"name2", <VALUE2>} > + } > + }) > + > +The UUID identifies contents of the following package. In case of ACPI > +device properties it is daffd814-6eba-4d8c-8a91-bc9bbf4aa301. > + > +In each returned package, the first item is the name and must be a string. > +The corresponding value can be a string, integer, reference, or package. If > +a package it may only contain strings, integers, and references. > + > +An example device where we might need properties is a device that uses > +GPIOs. In addition to the GpioIo/GpioInt resources the driver needs to > +know which GPIO is used for which purpose. > + > +To solve this we add the following ACPI device properties to the device: > + > + Device (DEV0) > + { > + Name (_CRS, ResourceTemplate () { > + GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly, > + "\\_SB.PCI0.LPC", 0, ResourceConsumer) {0} > + GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly, > + "\\_SB.PCI0.LPC", 0, ResourceConsumer) {1} > + ... > + }) > + > + Name (_DSD, Package () { > + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), > + Package () { > + Package () {"reset-gpio", {^DEV0, 0, 0, 0}}, > + Package () {"shutdown-gpio", {^DEV0, 1, 0, 0}}, > + } > + }) > + } > + > +Now the device driver can reference the GPIOs using names instead of > +using indexes. Ummm... so this is kind of odd. Why would arguments be needed for the gpio reference, or a device trying to reference itself (^DEV0) within it's own device. It looks like it is trying to shoehorn DT design patterns into the ACPI tables when ACPI already has a native method for doing the same thing. That concerns me. [...] > +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} > + } > + }) > + } > + > + Device (\_SB.PCI0.BL) > + { > + Name (_DSD, Package () { > + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), > + Package () { > + Package () { > + "pwms", > + Package () { > + \_SB.PCI0.PWM, 0, 5000000, > + \_SB.PCI0.PWM, 1, 4500000, > + } > + } > + } > + }) > + } This worries me even more. #x-cells is a very devicetree oriented pattern that looks wrong for ACPI data. I would expect PWM resources in ACPI to look much like ACPI GPIO resources or Serial bus resources. g. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
