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Commit cfc50764 authored by Mika Westerberg's avatar Mika Westerberg Committed by Jonathan Corbet
Browse files

Documentation: gpio: Update ACPI part of the document to mention _DSD 



With ACPI 5.1 _DSD (Device Specific Data) it is now possible to name
functions just like Device Tree is doing. Make sure that the documentation
mentions _DSD as the recommended way to describe GPIOs in ACPI systems.

Reported-by: default avatarDarren Hart <dvhart@linux.intel.com>
Reviewed-by: default avatarDarren Hart <dvhart@linux.intel.com>
Signed-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 7085f6c3

Documentation/gpio/board.txt

+37 −4
Original line number Diff line number Diff line
@@ -50,10 +50,43 @@ gpiod_is_active_low(power) will be true). 


ACPI

----

ACPI does not support function names for GPIOs. Therefore, only the "idx"

argument of gpiod_get_index() is useful to discriminate between GPIOs assigned

to a device. The "con_id" argument can still be set for debugging purposes (it

will appear under error messages as well as debug and sysfs nodes).

ACPI also supports function names for GPIOs in a similar fashion to DT.

The above DT example can be converted to an equivalent ACPI description

with the help of _DSD (Device Specific Data), introduced in ACPI 5.1:



	Device (FOO) {

		Name (_CRS, ResourceTemplate () {

			GpioIo (Exclusive, ..., IoRestrictionOutputOnly,

				"\\_SB.GPI0") {15} // red

			GpioIo (Exclusive, ..., IoRestrictionOutputOnly,

				"\\_SB.GPI0") {16} // green

			GpioIo (Exclusive, ..., IoRestrictionOutputOnly,

				"\\_SB.GPI0") {17} // blue

			GpioIo (Exclusive, ..., IoRestrictionOutputOnly,

				"\\_SB.GPI0") {1} // power

		})



		Name (_DSD, Package () {

			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),

			Package () {

				Package () {

					"led-gpios",

					Package () {

						^FOO, 0, 0, 1,

						^FOO, 1, 0, 1,

						^FOO, 2, 0, 1,

					}

				},

				Package () {

					"power-gpios",

					Package () {^FOO, 3, 0, 0},

				},

			}

		})

	}



For more information about the ACPI GPIO bindings see

Documentation/acpi/gpio-properties.txt.



Platform Data

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