acpi/dsd/leds.rst

1 .. SPDX-License-Identifier: GPL-2.0
9 device node, the LED driver chip. The "reg" property in the LED specific nodes
10 tells the numerical ID of each individual LED output to which the LEDs are
11 connected. [leds] The hierarchical data nodes are named "led@X", where X is the
12 number of the LED output.
14 Referring to LEDs in Device tree is documented in [video-interfaces], in
15 "flash-leds" property documentation. In short, LEDs are directly referred to by
20 the same mechanism on ACPI is not possible. A mechanism to refer to non-device
21 ACPI nodes is documented in [data-node-ref].
24 combination of the LED driver device reference and an integer argument,
25 referring to the "reg" property of the relevant LED, is used to identify
27 firmware and software, it uniquely identifies the LED driver outputs.
29 Under the LED driver device, The first hierarchical data extension package list
30 entry shall contain the string "led@" followed by the number of the LED,
31 followed by the referred object name. That object shall be named "LED" followed
32 by the number of the LED.
37 An ASL example of a camera sensor device and a LED driver device for two LEDs is
41 	Device (LED)
44 			ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
46 				Package () { "led@0", LED0 },
47 				Package () { "led@1", LED1 },
51 			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
54 				Package () { "flash-max-microamp", 1000000 },
55 				Package () { "flash-timeout-us", 200000 },
56 				Package () { "led-max-microamp", 100000 },
61 			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
64 				Package () { "led-max-microamp", 10000 },
73 			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
76 					"flash-leds",
77 					Package () { ^LED, "led@0", ^LED, "led@1" },
86 	LED	LED driver device
87 	LED0	First LED
88 	LED1	Second LED
89 	SEN	Camera sensor device (or another device the LED is related to)
95     https://uefi.org/specifications/ACPI/6.4/, referenced 2021-11-30.
97 [data-node-ref] Documentation/firmware-guide/acpi/dsd/data-node-references.rst
99 [devicetree] Devicetree. https://www.devicetree.org, referenced 2019-02-21.
101 [dsd-guide] DSD Guide.
102     https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced
103     2021-11-30.
107 [video-interfaces] Documentation/devicetree/bindings/media/video-interfaces.yaml