Documentation: ACPI: explain how to use gpio-line-names (4697958b) · Commits · 戴 / test

Documentation/firmware-guide/acpi/gpio-properties.rst

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		@@ -133,7 +133,61 @@ Example::

		- gpio-line-names

		Example::
		The ``gpio-line-names`` declaration is a list of strings ("names"), which
		describes each line/pin of a GPIO controller/expander. This list, contained in
		a package, must be inserted inside the GPIO controller declaration of an ACPI
		table (typically inside the DSDT). The ``gpio-line-names`` list must respect the
		following rules (see also the examples):

		- the first name in the list corresponds with the first line/pin of the GPIO
		controller/expander
		- the names inside the list must be consecutive (no "holes" are permitted)
		- the list can be incomplete and can end before the last GPIO line: in
		other words, it is not mandatory to fill all the GPIO lines
		- empty names are allowed (two quotation marks ``""`` correspond to an empty
		name)

		Example of a GPIO controller of 16 lines, with an incomplete list with two
		empty names::

		Package () {
		"gpio-line-names",
		Package () {
		"pin_0",
		"pin_1",
		"",
		"",
		"pin_3",
		"pin_4_push_button",
		}
		}

		At runtime, the above declaration produces the following result (using the
		"libgpiod" tools)::

		root@debian:~# gpioinfo gpiochip4
		gpiochip4 - 16 lines:
		line 0: "pin_0" unused input active-high
		line 1: "pin_1" unused input active-high
		line 2: unnamed unused input active-high
		line 3: unnamed unused input active-high
		line 4: "pin_3" unused input active-high
		line 5: "pin_4_push_button" unused input active-high
		line 6: unnamed unused input active-high
		line 7 unnamed unused input active-high
		line 8: unnamed unused input active-high
		line 9: unnamed unused input active-high
		line 10: unnamed unused input active-high
		line 11: unnamed unused input active-high
		line 12: unnamed unused input active-high
		line 13: unnamed unused input active-high
		line 14: unnamed unused input active-high
		line 15: unnamed unused input active-high
		root@debian:~# gpiofind pin_4_push_button
		gpiochip4 5
		root@debian:~#

		Another example::

		Package () {
		"gpio-line-names",

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