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Documentation / devicetree / bindings / leds / common.txt




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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:55 EST.

1	* Common leds properties.
2	
3	LED and flash LED devices provide the same basic functionality as current
4	regulators, but extended with LED and flash LED specific features like
5	blinking patterns, flash timeout, flash faults and external flash strobe mode.
6	
7	Many LED devices expose more than one current output that can be connected
8	to one or more discrete LED component. Since the arrangement of connections
9	can influence the way of the LED device initialization, the LED components
10	have to be tightly coupled with the LED device binding. They are represented
11	by child nodes of the parent LED device binding.
12	
13	Optional properties for child nodes:
14	- led-sources : List of device current outputs the LED is connected to. The
15			outputs are identified by the numbers that must be defined
16			in the LED device binding documentation.
17	- label : The label for this LED. If omitted, the label is taken from the node
18		  name (excluding the unit address). It has to uniquely identify
19		  a device, i.e. no other LED class device can be assigned the same
20		  label.
21	
22	- default-state : The initial state of the LED. Valid values are "on", "off",
23	  and "keep". If the LED is already on or off and the default-state property is
24	  set the to same value, then no glitch should be produced where the LED
25	  momentarily turns off (or on). The "keep" setting will keep the LED at
26	  whatever its current state is, without producing a glitch.  The default is
27	  off if this property is not present.
28	
29	- linux,default-trigger :  This parameter, if present, is a
30	    string defining the trigger assigned to the LED.  Current triggers are:
31	     "backlight" - LED will act as a back-light, controlled by the framebuffer
32			   system
33	     "default-on" - LED will turn on (but for leds-gpio see "default-state"
34			    property in Documentation/devicetree/bindings/gpio/led.txt)
35	     "heartbeat" - LED "double" flashes at a load average based rate
36	     "disk-activity" - LED indicates disk activity
37	     "ide-disk" - LED indicates IDE disk activity (deprecated),
38	                  in new implementations use "disk-activity"
39	     "timer" - LED flashes at a fixed, configurable rate
40	
41	- led-max-microamp : Maximum LED supply current in microamperes. This property
42	                     can be made mandatory for the board configurations
43	                     introducing a risk of hardware damage in case an excessive
44	                     current is set.
45	                     For flash LED controllers with configurable current this
46	                     property is mandatory for the LEDs in the non-flash modes
47	                     (e.g. torch or indicator).
48	
49	- panic-indicator : This property specifies that the LED should be used,
50			    if at all possible, as a panic indicator.
51	
52	- trigger-sources : List of devices which should be used as a source triggering
53			    this LED activity. Some LEDs can be related to a specific
54			    device and should somehow indicate its state. E.g. USB 2.0
55			    LED may react to device(s) in a USB 2.0 port(s).
56			    Another common example is switch or router with multiple
57			    Ethernet ports each of them having its own LED assigned
58			    (assuming they are not hardwired). In such cases this
59			    property should contain phandle(s) of related source
60			    device(s).
61			    In many cases LED can be related to more than one device
62			    (e.g. one USB LED vs. multiple USB ports). Each source
63			    should be represented by a node in the device tree and be
64			    referenced by a phandle and a set of phandle arguments. A
65			    length of arguments should be specified by the
66			    #trigger-source-cells property in the source node.
67	
68	Required properties for flash LED child nodes:
69	- flash-max-microamp : Maximum flash LED supply current in microamperes.
70	- flash-max-timeout-us : Maximum timeout in microseconds after which the flash
71	                         LED is turned off.
72	
73	For controllers that have no configurable current the flash-max-microamp
74	property can be omitted.
75	For controllers that have no configurable timeout the flash-max-timeout-us
76	property can be omitted.
77	
78	* Trigger source providers
79	
80	Each trigger source should be represented by a device tree node. It may be e.g.
81	a USB port or an Ethernet device.
82	
83	Required properties for trigger source:
84	- #trigger-source-cells : Number of cells in a source trigger. Typically 0 for
85				  nodes of simple trigger sources (e.g. a specific USB
86				  port).
87	
88	* Examples
89	
90	gpio-leds {
91		compatible = "gpio-leds";
92	
93		system-status {
94			label = "Status";
95			linux,default-trigger = "heartbeat";
96			gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
97		};
98	
99		usb {
100			gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
101			trigger-sources = <&ohci_port1>, <&ehci_port1>;
102		};
103	};
104	
105	max77693-led {
106		compatible = "maxim,max77693-led";
107	
108		camera-flash {
109			label = "Flash";
110			led-sources = <0>, <1>;
111			led-max-microamp = <50000>;
112			flash-max-microamp = <320000>;
113			flash-max-timeout-us = <500000>;
114		};
115	};
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