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authorDuncan Laurie <dlaurie@chromium.org>2016-05-10 13:18:17 -0700
committerDuncan Laurie <dlaurie@google.com>2016-05-28 03:48:55 +0200
commit559e947306d9a8684f7c0879c122a9b3b3f87c16 (patch)
tree69da36f121c27acf2704a7343ad47ae2a01dd870 /src/mainboard
parent70c86d9b265a7ea821fcd1b0684d60393d9908c1 (diff)
acpi_device: Add support for writing ACPI Device Properties
The recent ACPI specification extensions have formally defined a method for describing device information with a key=value format that is modeled after the Devicetree/DTS format using a special crafted object named _DSD with a specific UUID for this format. There are three defined Device Property types: Integers, Strings, and References. It is also possible to have arrays of these properties under one key=value pair. Strings and References are both represented as character arrays but result in different generated ACPI OpCodes. Various helpers are provided for writing the Device Property header (to fill in the object name and UUID) and footer (to fill in the property count and device length values) as well as for writing the different Device Property types. A specific helper is provided for writing the defined GPIO binding Device Property that is used to allow GPIOs to be referred to by name rather than resource index. This is all documented in the _DSD Device Properties UUID document: http://uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf This will be used by device drivers to provide device properties that are consumed by the operating system. Devicetree bindings are often described in the linux kernel at Documentation/devicetree/bindings/ A sample driver here has an input GPIO that it needs to describe to the kernel driver: chip.h: struct drivers_generic_sample_config { struct acpi_gpio mode_gpio; }; sample.c: static void acpi_fill_ssdt_generator(struct device *dev) { struct drivers_generic_sample_config *config = dev->chip_info; const char *path = acpi_device_path(dev); ... acpi_device_write_gpio(&config->mode_gpio); ... acpi_dp_write_header(); acpi_dp_write_gpio("mode-gpio", path, 0, 0, 0); acpi_dp_write_footer(); ... } devicetree.cb: device pci 1f.0 on chip drivers/generic/sample register "mode_gpio" = "ACPI_GPIO_INPUT(GPP_B1)" device generic 0 on end end end SSDT.dsl: Name (_CRS, ResourceTemplate () { GpioIo (Exclusive, PullDefault, 0, 0, IoRestrictionInputOnly, "\\_SB.PCI0.GPIO", 0, ResourceConsumer) { 25 } }) Name (_DSD, Package () { ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), Package () { Package () {"mode-gpio", Package () { \_SB.PCI0.LPCB, 0, 0, 1 }} } }) Change-Id: I93ffd09e59d05c09e38693e221a87085469be3ad Signed-off-by: Duncan Laurie <dlaurie@chromium.org> Reviewed-on: https://review.coreboot.org/14937 Tested-by: build bot (Jenkins) Reviewed-by: Aaron Durbin <adurbin@chromium.org>
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