LED

If you are using Linux as your kernel on a SoC design, you’ll be glad to know that it has an entire subsystem dedicated to LEDs! Fabio Baltieri Linux LED Subsystem

Linux Kernel GPIO Documentation

menuconfig LEDS_TRIGGERS
    bool "LED Trigger support"
    depends on LEDS_CLASS
    help
      This option enables trigger support for the leds class.
      These triggers allow kernel events to drive the LEDs and can
      be configured via sysfs. If unsure, say Y.

if LEDS_TRIGGERS

...

config LEDS_TRIGGER_HEARTBEAT
    tristate "LED Heartbeat Trigger"
    depends on LEDS_TRIGGERS
    help
      This allows LEDs to be controlled by a CPU load average.
      The flash frequency is a hyperbolic function of the 1-minute
      load average.
      If unsure, say Y.

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