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authorPavel Machek <pavel@ucw.cz>2021-08-20 11:26:24 +0300
committerPavel Machek <pavel@ucw.cz>2021-08-20 11:26:24 +0300
commit09f1273064eea23ec41fb206f6eccc2bf79d1fa1 (patch)
tree3c464261fffaa1970792146387045e24bf54d4aa /Documentation
parent5358680e675744962a8adc99263adf59adfa8960 (diff)
downloadlinux-09f1273064eea23ec41fb206f6eccc2bf79d1fa1.tar.xz
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>
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+-*- 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)