About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / devicetree / bindings / leds / common.txt




Custom Search

Based on kernel version 4.9. Page generated on 2016-12-21 14:30 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	Required properties for flash LED child nodes:
53	- flash-max-microamp : Maximum flash LED supply current in microamperes.
54	- flash-max-timeout-us : Maximum timeout in microseconds after which the flash
55	                         LED is turned off.
56	
57	For controllers that have no configurable current the flash-max-microamp
58	property can be omitted.
59	For controllers that have no configurable timeout the flash-max-timeout-us
60	property can be omitted.
61	
62	Examples:
63	
64	system-status {
65		label = "Status";
66		linux,default-trigger = "heartbeat";
67		...
68	};
69	
70	camera-flash {
71		label = "Flash";
72		led-sources = <0>, <1>;
73		led-max-microamp = <50000>;
74		flash-max-microamp = <320000>;
75		flash-max-timeout-us = <500000>;
76	};
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.