116 lines
4.8 KiB
Plaintext
116 lines
4.8 KiB
Plaintext
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* Common leds properties.
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LED and flash LED devices provide the same basic functionality as current
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regulators, but extended with LED and flash LED specific features like
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blinking patterns, flash timeout, flash faults and external flash strobe mode.
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Many LED devices expose more than one current output that can be connected
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to one or more discrete LED component. Since the arrangement of connections
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can influence the way of the LED device initialization, the LED components
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have to be tightly coupled with the LED device binding. They are represented
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by child nodes of the parent LED device binding.
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Optional properties for child nodes:
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- led-sources : List of device current outputs the LED is connected to. The
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outputs are identified by the numbers that must be defined
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in the LED device binding documentation.
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- label : The label for this LED. If omitted, the label is taken from the node
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name (excluding the unit address). It has to uniquely identify
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a device, i.e. no other LED class device can be assigned the same
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label.
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- default-state : The initial state of the LED. Valid values are "on", "off",
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and "keep". If the LED is already on or off and the default-state property is
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set the to same value, then no glitch should be produced where the LED
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momentarily turns off (or on). The "keep" setting will keep the LED at
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whatever its current state is, without producing a glitch. The default is
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off if this property is not present.
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- linux,default-trigger : This parameter, if present, is a
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string defining the trigger assigned to the LED. Current triggers are:
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"backlight" - LED will act as a back-light, controlled by the framebuffer
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system
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"default-on" - LED will turn on (but for leds-gpio see "default-state"
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property in Documentation/devicetree/bindings/leds/leds-gpio.txt)
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"heartbeat" - LED "double" flashes at a load average based rate
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"disk-activity" - LED indicates disk activity
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"ide-disk" - LED indicates IDE disk activity (deprecated),
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in new implementations use "disk-activity"
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"timer" - LED flashes at a fixed, configurable rate
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- led-max-microamp : Maximum LED supply current in microamperes. This property
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can be made mandatory for the board configurations
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introducing a risk of hardware damage in case an excessive
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current is set.
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For flash LED controllers with configurable current this
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property is mandatory for the LEDs in the non-flash modes
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(e.g. torch or indicator).
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- panic-indicator : This property specifies that the LED should be used,
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if at all possible, as a panic indicator.
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- trigger-sources : List of devices which should be used as a source triggering
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this LED activity. Some LEDs can be related to a specific
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device and should somehow indicate its state. E.g. USB 2.0
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LED may react to device(s) in a USB 2.0 port(s).
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Another common example is switch or router with multiple
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Ethernet ports each of them having its own LED assigned
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(assuming they are not hardwired). In such cases this
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property should contain phandle(s) of related source
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device(s).
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In many cases LED can be related to more than one device
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(e.g. one USB LED vs. multiple USB ports). Each source
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should be represented by a node in the device tree and be
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referenced by a phandle and a set of phandle arguments. A
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length of arguments should be specified by the
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#trigger-source-cells property in the source node.
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Required properties for flash LED child nodes:
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- flash-max-microamp : Maximum flash LED supply current in microamperes.
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- flash-max-timeout-us : Maximum timeout in microseconds after which the flash
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LED is turned off.
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For controllers that have no configurable current the flash-max-microamp
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property can be omitted.
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For controllers that have no configurable timeout the flash-max-timeout-us
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property can be omitted.
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* Trigger source providers
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Each trigger source should be represented by a device tree node. It may be e.g.
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a USB port or an Ethernet device.
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Required properties for trigger source:
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- #trigger-source-cells : Number of cells in a source trigger. Typically 0 for
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nodes of simple trigger sources (e.g. a specific USB
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port).
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* Examples
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gpio-leds {
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compatible = "gpio-leds";
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system-status {
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label = "Status";
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linux,default-trigger = "heartbeat";
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gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
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};
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usb {
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gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
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trigger-sources = <&ohci_port1>, <&ehci_port1>;
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};
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};
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max77693-led {
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compatible = "maxim,max77693-led";
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camera-flash {
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label = "Flash";
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led-sources = <0>, <1>;
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led-max-microamp = <50000>;
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flash-max-microamp = <320000>;
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flash-max-timeout-us = <500000>;
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};
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};
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