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Some LEDs can be related to a specific device(s) described in the DT. This property allows specifying such relations. E.g. USB LED should usually be used to indicate some USB port(s) state. Please note this binding is designed to be generic and not influenced by any operating system design. Linux developers may find "trigger" part a bit confusing since in Linux triggers are separated drivers. It shouldn't define the binding though (we shouldn't add an extra level of indirection). Signed-off-by: Rafał Miłecki <rafal@milecki.pl> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
116 lines
4.8 KiB
Plaintext
116 lines
4.8 KiB
Plaintext
* 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/gpio/led.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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