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

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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: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mika Westerberg 2015-04-01 11:13:16 +03:00 committed by Jonathan Corbet
parent 7085f6c354
commit cfc507648c
1 changed files with 37 additions and 4 deletions
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41
Documentation/gpio/board.txt
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@ -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
-------------