Documentation: leds: standartizing LED names

We have a list of valid functions, but LED names in sysfs are still
far from being consistent. Create list of "well known" LED names so we
nudge people towards using same LED names (except color) for same
functionality.

Signed-off-by: Pavel Machek <pavel@ucw.cz>
This commit is contained in:
Pavel Machek 2021-08-20 10:26:24 +02:00
parent 5358680e67
commit 09f1273064

View File

@ -0,0 +1,58 @@
-*- org -*-
It is somehow important to provide consistent interface to the
userland. LED devices have one problem there, and that is naming of
directories in /sys/class/leds. It would be nice if userland would
just know right "name" for given LED function, but situation got more
complex.
Anyway, if backwards compatibility is not an issue, new code should
use one of the "good" names from this list, and you should extend the
list where applicable.
Legacy names are listed, too; in case you are writing application that
wants to use particular feature, you should probe for good name, first,
but then try the legacy ones, too.
Notice there's a list of functions in include/dt-bindings/leds/common.h .
* Keyboards
Good: "input*:*:capslock"
Good: "input*:*:scrolllock"
Good: "input*:*:numlock"
Legacy: "shift-key-light" (Motorola Droid 4, capslock)
Set of common keyboard LEDs, going back to PC AT or so.
Legacy: "tpacpi::thinklight" (IBM/Lenovo Thinkpads)
Legacy: "lp5523:kb{1,2,3,4,5,6}" (Nokia N900)
Frontlight/backlight of main keyboard.
Legacy: "button-backlight" (Motorola Droid 4)
Some phones have touch buttons below screen; it is different from main
keyboard. And this is their backlight.
* Sound subsystem
Good: "platform:*:mute"
Good: "platform:*:micmute"
LEDs on notebook body, indicating that sound input / output is muted.
* System notification
Legacy: "status-led:{red,green,blue}" (Motorola Droid 4)
Legacy: "lp5523:{r,g,b}" (Nokia N900)
Phones usually have multi-color status LED.
* Power management
Good: "platform:*:charging" (allwinner sun50i)
* Screen
Good: ":backlight" (Motorola Droid 4)