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-rw-r--r--Documentation/gpio/board.txt41
1 files changed, 37 insertions, 4 deletions
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
index 8b35f51fe7b6..b80606de545a 100644
--- a/Documentation/gpio/board.txt
+++ b/Documentation/gpio/board.txt
@@ -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
-------------