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authorSakari Ailus <sakari.ailus@linux.intel.com>2019-08-14 15:58:58 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-08-20 23:53:46 +0200
commit2b2d4247e445b97113c5e61df8fbc0d756482ef8 (patch)
treee0950a41d699fb2fcf95b0526d2dc889851be816 /Documentation/firmware-guide
parentd1abaeb3be7b5fa6d7a1fbbd2e14e3310005c4c1 (diff)
downloadlinux-2b2d4247e445b97113c5e61df8fbc0d756482ef8.tar.bz2
Documentation: ACPI: DSD: Convert LED documentation to ReST
Convert the LED documentation in text format into ReST. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/firmware-guide')
-rw-r--r--Documentation/firmware-guide/acpi/dsd/leds.rst111
-rw-r--r--Documentation/firmware-guide/acpi/index.rst1
2 files changed, 112 insertions, 0 deletions
diff --git a/Documentation/firmware-guide/acpi/dsd/leds.rst b/Documentation/firmware-guide/acpi/dsd/leds.rst
new file mode 100644
index 000000000000..946efe2b2936
--- /dev/null
+++ b/Documentation/firmware-guide/acpi/dsd/leds.rst
@@ -0,0 +1,111 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+========================================
+Describing and referring to LEDs in ACPI
+========================================
+
+Individual LEDs are described by hierarchical data extension [6] nodes under the
+device node, the LED driver chip. The "reg" property in the LED specific nodes
+tells the numerical ID of each individual LED output to which the LEDs are
+connected. [3] The hierarchical data nodes are named "led@X", where X is the
+number of the LED output.
+
+Referring to LEDs in Device tree is documented in [4], in "flash-leds" property
+documentation. In short, LEDs are directly referred to by using phandles.
+
+While Device tree allows referring to any node in the tree[1], in ACPI
+references are limited to device nodes only [2]. For this reason using the same
+mechanism on ACPI is not possible. A mechanism to refer to non-device ACPI nodes
+is documented in [7].
+
+ACPI allows (as does DT) using integer arguments after the reference. A
+combination of the LED driver device reference and an integer argument,
+referring to the "reg" property of the relevant LED, is used to identify
+individual LEDs. The value of the "reg" property is a contract between the
+firmware and software, it uniquely identifies the LED driver outputs.
+
+Under the LED driver device, The first hierarchical data extension package list
+entry shall contain the string "led@" followed by the number of the LED,
+followed by the referred object name. That object shall be named "LED" followed
+by the number of the LED.
+
+Example
+=======
+
+An ASL example of a camera sensor device and a LED driver device for two LEDs is
+show below. Objects not relevant for LEDs or the references to them have been
+omitted. ::
+
+ Device (LED)
+ {
+ Name (_DSD, Package () {
+ ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+ Package () {
+ Package () { "led@0", LED0 },
+ Package () { "led@1", LED1 },
+ }
+ })
+ Name (LED0, Package () {
+ ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ Package () {
+ Package () { "reg", 0 },
+ Package () { "flash-max-microamp", 1000000 },
+ Package () { "flash-timeout-us", 200000 },
+ Package () { "led-max-microamp", 100000 },
+ Package () { "label", "white:flash" },
+ }
+ })
+ Name (LED1, Package () {
+ ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ Package () {
+ Package () { "reg", 1 },
+ Package () { "led-max-microamp", 10000 },
+ Package () { "label", "red:indicator" },
+ }
+ })
+ }
+
+ Device (SEN)
+ {
+ Name (_DSD, Package () {
+ ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ Package () {
+ Package () {
+ "flash-leds",
+ Package () { ^LED, "led@0", ^LED, "led@1" },
+ }
+ }
+ })
+ }
+
+where
+::
+
+ LED LED driver device
+ LED0 First LED
+ LED1 Second LED
+ SEN Camera sensor device (or another device the LED is related to)
+
+References
+==========
+
+[1] Device tree. <URL:http://www.devicetree.org>, referenced 2019-02-21.
+
+[2] Advanced Configuration and Power Interface Specification.
+ <URL:https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf>,
+ referenced 2019-02-21.
+
+[3] Documentation/devicetree/bindings/leds/common.txt
+
+[4] Documentation/devicetree/bindings/media/video-interfaces.txt
+
+[5] Device Properties UUID For _DSD.
+ <URL:http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>,
+ referenced 2019-02-21.
+
+[6] Hierarchical Data Extension UUID For _DSD.
+ <URL:http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf>,
+ referenced 2019-02-21.
+
+[7] Documentation/firmware-guide/acpi/dsd/data-node-references.rst
diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst
index 90c90d42d9ad..ad3b5afdae77 100644
--- a/Documentation/firmware-guide/acpi/index.rst
+++ b/Documentation/firmware-guide/acpi/index.rst
@@ -10,6 +10,7 @@ ACPI Support
namespace
dsd/graph
dsd/data-node-references
+ dsd/leds
enumeration
osi
method-customizing