path: root/Documentation/leds
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authorLinus Torvalds <>2020-08-05 19:24:27 -0700
committerLinus Torvalds <>2020-08-05 19:24:27 -0700
commite4a7b2dc35d9582c253cf5e6d6c3605aabc7284d (patch)
treeaad09e47f8503053b94f7d330fced3d9d63a8b7a /Documentation/leds
parentfffe3ae0ee84e25d2befe2ae59bc32aa2b6bc77b (diff)
parentbba37471de2d7733b0deef57e03c47fa97a284a7 (diff)
Merge tag 'leds-5.9-rc1' of git://
Pull LED updates from Pavel Machek: "Okay, so... this one is interesting. RGB LEDs are very common, and we need to have some kind of support for them. Multicolor is for arbitrary set of LEDs in one package, RGB is for LEDs that can produce full range of colors. We do not have real multicolor LED that is not RGB in the pipeline, so that one is disabled for now. You can expect this saga to continue with next pull requests" * tag 'leds-5.9-rc1' of git:// (37 commits) MAINTAINERS: Remove myself as LED subsystem maintainer leds: disallow /sys/class/leds/*:multi:* for now leds: add RGB color option, as that is different from multicolor. Make LEDS_LP55XX_COMMON depend on I2C to fix build errors: Documentation: ABI: leds-turris-omnia: document sysfs attribute leds: initial support for Turris Omnia LEDs dt-bindings: leds: add cznic,turris-omnia-leds binding leds: pattern trigger -- check pattern for validity leds: Replace HTTP links with HTTPS ones leds: trigger: add support for LED-private device triggers leds: lp5521: Add multicolor framework multicolor brightness support leds: lp5523: Update the lp5523 code to add multicolor brightness function leds: lp55xx: Add multicolor framework support to lp55xx leds: lp55xx: Convert LED class registration to devm_* dt-bindings: leds: Convert leds-lp55xx to yaml leds: multicolor: Introduce a multicolor class definition leds: Add multicolor ID to the color ID list dt: bindings: Add multicolor class dt bindings documention leds: lp5523: Fix various formatting issues in the code leds: lp55xx: Fix file permissions to use DEVICE_ATTR macros ...
Diffstat (limited to 'Documentation/leds')
2 files changed, 87 insertions, 0 deletions
diff --git a/Documentation/leds/index.rst b/Documentation/leds/index.rst
index 060f4e485897..bc70c6aa7138 100644
--- a/Documentation/leds/index.rst
+++ b/Documentation/leds/index.rst
@@ -9,6 +9,7 @@ LEDs
+ leds-class-multicolor
diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
new file mode 100644
index 000000000000..c57b98bfd387
--- /dev/null
+++ b/Documentation/leds/leds-class-multicolor.rst
@@ -0,0 +1,86 @@
+.. SPDX-License-Identifier: GPL-2.0
+Multicolor LED handling under Linux
+The multicolor class groups monochrome LEDs and allows controlling two
+aspects of the final combined color: hue and lightness. The former is
+controlled via the multi_intensity array file and the latter is controlled
+via brightness file.
+Multicolor Class Control
+The multicolor class presents files that groups the colors as indexes in an
+array. These files are children under the LED parent node created by the
+led_class framework. The led_class framework is documented in led-class.rst
+within this documentation directory.
+Each colored LED will be indexed under the multi_* files. The order of the
+colors will be arbitrary. The multi_index file can be read to determine the
+color name to indexed value.
+The multi_index file is an array that contains the string list of the colors as
+they are defined in each multi_* array file.
+The multi_intensity is an array that can be read or written to for the
+individual color intensities. All elements within this array must be written in
+order for the color LED intensities to be updated.
+Directory Layout Example
+root:/sys/class/leds/multicolor:status# ls -lR
+-rw-r--r-- 1 root root 4096 Oct 19 16:16 brightness
+-r--r--r-- 1 root root 4096 Oct 19 16:16 max_brightness
+-r--r--r-- 1 root root 4096 Oct 19 16:16 multi_index
+-rw-r--r-- 1 root root 4096 Oct 19 16:16 multi_intensity
+Multicolor Class Brightness Control
+The brightness level for each LED is calculated based on the color LED
+intensity setting divided by the global max_brightness setting multiplied by
+the requested brightness.
+led_brightness = brightness * multi_intensity/max_brightness
+A user first writes the multi_intensity file with the brightness levels
+for each LED that are necessary to achieve a certain color output from a
+multicolor LED group.
+cat /sys/class/leds/multicolor:status/multi_index
+green blue red
+echo 43 226 138 > /sys/class/leds/multicolor:status/multi_intensity
+red -
+ intensity = 138
+ max_brightness = 255
+green -
+ intensity = 43
+ max_brightness = 255
+blue -
+ intensity = 226
+ max_brightness = 255
+The user can control the brightness of that multicolor LED group by writing the
+global 'brightness' control. Assuming a max_brightness of 255 the user
+may want to dim the LED color group to half. The user would write a value of
+128 to the global brightness file then the values written to each LED will be
+adjusted base on this value.
+cat /sys/class/leds/multicolor:status/max_brightness
+echo 128 > /sys/class/leds/multicolor:status/brightness
+adjusted_red_value = 128 * 138/255 = 69
+adjusted_green_value = 128 * 43/255 = 21
+adjusted_blue_value = 128 * 226/255 = 113
+Reading the global brightness file will return the current brightness value of
+the color LED group.
+cat /sys/class/leds/multicolor:status/brightness