Keyboard backlighting

[sidetone]

Keyboard backlighting for typing in the dark, for coolness and/or for gaming.

For controlling individual LED lights, there's xset(1) (different from xsetroot):
led

The led option controls the keyboard LEDs. This controls the
turning on or off of one or all of the LEDs. It accepts an
optional integer, a preceding dash(-) or an 'on/off' flag. If
no parameter or the 'on' flag is given, all LEDs are turned on.
If a preceding dash or the flag 'off' is given, all LEDs are
turned off. If a value between 1 and 32 is given, that LED
will be turned on or off depending on the existence of a
preceding dash. ``xset led 3'' would turn led #3 on. ``xset
-led 3'' would turn it off. The particular LED values may
refer to different LEDs on different hardware. If the X server
supports the XKEYBOARD (XKB) extension, leds may be referenced
by the XKB indicator name by specifying the `named' keyword and
the indicator name. For example, to turn on the Scroll Lock
LED:

xset led named "Scroll Lock"
x11/xset is also used for controlling power management (DPMS) for monitors (standby/suspend/on/off).

For led controls of ASUS backlit keyboards there's Thread asus-rgb-keyboard-backlight.82111. Thread general-backlit-keyboard-enabling-instructions.62614 mentions an older HID driver, with no all-around solution, because of reliance on proprietary drivers. It mentions using BIOS settings for hardware with that capability. Ideally, keyboard drivers would fundamentally rely on the newer USBHID. For newer threads, please add the respective tag: https://forums.freebsd.org/tags/keyboard-backlight/