1 files changed, 103 insertions, 0 deletions
diff --git a/Documentation/leds/well-known-leds.txt b/Documentation/leds/well-known-leds.txt
new file mode 100644
index 0000000000..67b4470480
--- /dev/null
+++ b/Documentation/leds/well-known-leds.txt
@@ -0,0 +1,103 @@
+-*- 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 .
+
+* Gamepads and joysticks
+
+Game controllers may feature LEDs to indicate a player number. This is commonly
+used on game consoles in which multiple controllers can be connected to a system.
+The "player LEDs" are then programmed with a pattern to indicate a particular
+player. For example, a game controller with 4 LEDs, may be programmed with "x---"
+to indicate player 1, "-x--" to indicate player 2 etcetera where "x" means on.
+Input drivers can utilize the LED class to expose the individual player LEDs
+of a game controller using the function "player".
+Note: tracking and management of Player IDs is the responsibility of user space,
+though drivers may pick a default value.
+
+Good: "input*:*:player-{1,2,3,4,5}
+
+* 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
+
+Good: "rgb:status"
+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, leds-cht-wcove)
+
+* Screen
+
+Good: ":backlight" (Motorola Droid 4)
+
+* Ethernet LEDs
+
+Currently two types of Network LEDs are support, those controlled by
+the PHY and those by the MAC. In theory both can be present at the
+same time for one Linux netdev, hence the names need to differ between
+MAC and PHY.
+
+Do not use the netdev name, such as eth0, enp1s0. These are not stable
+and are not unique. They also don't differentiate between MAC and PHY.
+
+** MAC LEDs
+
+Good: f1070000.ethernet:white:WAN
+Good: mdio_mux-0.1:00:green:left
+Good: 0000:02:00.0:yellow:top
+
+The first part must uniquely name the MAC controller. Then follows the
+colour.  WAN/LAN should be used for a single LED. If there are
+multiple LEDs, use left/right, or top/bottom to indicate their
+position on the RJ45 socket.
+
+** PHY LEDs
+
+Good: f1072004.mdio-mii:00: white:WAN
+Good: !mdio-mux!mdio@2!switch@0!mdio:01:green:right
+Good: r8169-0-200:00:yellow:bottom
+
+The first part must uniquely name the PHY. This often means uniquely
+identifying the MDIO bus controller, and the address on the bus.