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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 +==================================== + +Description +=========== +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 + +Example: +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 +255 +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 +128 |