path: root/Documentation/leds
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authorJacek Anaszewski <>2019-06-09 20:19:04 +0200
committerJacek Anaszewski <>2019-07-25 20:07:52 +0200
commitbb4e9af0348dfeafd66c7e7f82e8a0983fe5390c (patch)
treeaa041503eb63871045847a4f84ad14fa2988dbd3 /Documentation/leds
parentc5d18dd6b64e09dd6984bda9bdd55160af537a8c (diff)
leds: core: Add support for composing LED class device names
Add generic support for composing LED class device name. The newly introduced led_compose_name() function composes device name according to either <color:function> or <devicename:color:function> pattern, depending on the configuration of initialization data. Backward compatibility with in-driver hard-coded LED class device names is assured thanks to the default_label and devicename properties of newly introduced struct led_init_data. In case none of the aforementioned properties was found, then, for OF nodes, the node name is adopted for LED class device name. At the occassion of amending the Documentation/leds/leds-class.txt unify spelling: colour -> color. Alongside these changes added is a new tool - tools/leds/ The tool allows retrieving details of a LED class device's parent device, which proves that using vendor or product name for devicename part of LED name doesn't convey any added value since that information had been already available in sysfs. The script performs also basic validation of a LED class device name. Signed-off-by: Jacek Anaszewski <> Cc: Baolin Wang <> Cc: Dan Murphy <> Cc: Daniel Mack <> Cc: Linus Walleij <> Cc: Oleh Kravchenko <> Cc: Sakari Ailus <> Cc: Simon Shields <> Reviewed-by: Linus Walleij <> Acked-by: Pavel Machek <>
Diffstat (limited to 'Documentation/leds')
1 files changed, 67 insertions, 3 deletions
diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
index df0120a1ee3c..a0708d3f3d0b 100644
--- a/Documentation/leds/leds-class.rst
+++ b/Documentation/leds/leds-class.rst
@@ -43,9 +43,73 @@ LED Device Naming
Is currently of the form:
- "devicename:colour:function"
-There have been calls for LED properties such as colour to be exported as
+ "devicename:color:function"
+- devicename:
+ it should refer to a unique identifier created by the kernel,
+ like e.g. phyN for network devices or inputN for input devices, rather
+ than to the hardware; the information related to the product and the bus
+ to which given device is hooked is available in sysfs and can be
+ retrieved using script from tools/leds; generally
+ this section is expected mostly for LEDs that are somehow associated with
+ other devices.
+- color:
+ one of LED_COLOR_ID_* definitions from the header
+ include/dt-bindings/leds/common.h.
+- function:
+ one of LED_FUNCTION_* definitions from the header
+ include/dt-bindings/leds/common.h.
+If required color or function is missing, please submit a patch
+It is possible that more than one LED with the same color and function will
+be required for given platform, differing only with an ordinal number.
+In this case it is preferable to just concatenate the predefined LED_FUNCTION_*
+name with required "-N" suffix in the driver. fwnode based drivers can use
+function-enumerator property for that and then the concatenation will be handled
+automatically by the LED core upon LED class device registration.
+LED subsystem has also a protection against name clash, that may occur
+when LED class device is created by a driver of hot-pluggable device and
+it doesn't provide unique devicename section. In this case numerical
+suffix (e.g. "_1", "_2", "_3" etc.) is added to the requested LED class
+device name.
+There might be still LED class drivers around using vendor or product name
+for devicename, but this approach is now deprecated as it doesn't convey
+any added value. Product information can be found in other places in sysfs
+(see tools/leds/
+Examples of proper LED names:
+ - "red:disk"
+ - "white:flash"
+ - "red:indicator"
+ - "phy1:green:wlan"
+ - "phy3::wlan"
+ - ":kbd_backlight"
+ - "input5::kbd_backlight"
+ - "input3::numlock"
+ - "input3::scrolllock"
+ - "input3::capslock"
+ - "mmc1::status"
+ - "white:status"
+ script can be used for verifying if the LED name
+meets the requirements pointed out here. It performs validation of the LED class
+devicename sections and gives hints on expected value for a section in case
+the validation fails for it. So far the script supports validation
+of associations between LEDs and following types of devices:
+ - input devices
+ - ieee80211 compliant USB devices
+The script is open to extensions.
+There have been calls for LED properties such as color to be exported as
individual led class attributes. As a solution which doesn't incur as much
overhead, I suggest these become part of the device name. The naming scheme
above leaves scope for further attributes should they be needed. If sections