Add a documentation of LED Multicolor LED class specific
sysfs attributes.
Add multicolor framework class documentation describing the
usage of the files created.
Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
---
.../ABI/testing/sysfs-class-led-multicolor | 35 +++++++
Documentation/leds/index.rst | 1 +
Documentation/leds/leds-class-multicolor.rst | 96 +++++++++++++++++++
3 files changed, 132 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-class-led-multicolor
create mode 100644 Documentation/leds/leds-class-multicolor.rst
diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
new file mode 100644
index 000000000000..65cb43de26e6
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
@@ -0,0 +1,35 @@
+What: /sys/class/leds/<led>/brightness
+Date: Sept 2019
+KernelVersion: 5.5
+Contact: Dan Murphy <dmurphy@xxxxxx>
+Description: read/write
+ Writing to this file will update all LEDs within the group to a
+ calculated percentage of what each color LED intensity is set
+ to. The percentage is calculated via the equation below:
+
+ led_brightness = brightness * <color>_intensity/<color>_max_intensity
+
+ For additional details please refer to
+ Documentation/leds/leds-class-multicolor.rst.
+
+ The value of the color is from 0 to
+ /sys/class/leds/<led>/max_brightness.
+
+What: /sys/class/leds/<led>/colors/<color>_intensity
+Date: Sept 2019
+KernelVersion: 5.5
+Contact: Dan Murphy <dmurphy@xxxxxx>
+Description: read/write
+ The <color>_intensity file is created based on the color
+ defined by the registrar of the class.
+ There is one file per color presented.
+
+ The value of the color is from 0 to
+ /sys/class/leds/<led>/colors/<color>_max_intensity.
+
+What: /sys/class/leds/<led>/colors/<color>_max_intensity
+Date: Sept 2019
+KernelVersion: 5.5
+Contact: Dan Murphy <dmurphy@xxxxxx>
+Description: read only
+ Maximum intensity level for the LED color.
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
leds-class-flash
+ leds-class-multicolor
ledtrig-oneshot
ledtrig-transient
ledtrig-usbport
diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
new file mode 100644
index 000000000000..87a1588d7619
--- /dev/null
+++ b/Documentation/leds/leds-class-multicolor.rst
@@ -0,0 +1,96 @@
+====================================
+Multi Color LED handling under Linux
+====================================
+
+Description
+===========
+The multi color class groups monochrome LEDs and allows controlling two
+aspects of the final combined color: hue and lightness. The former is
+controlled via <color>_intensity files and the latter is controlled
+via brightness file.
+
+For more details on hue and lightness notions please refer to
+https://en.wikipedia.org/wiki/CIECAM02.
+
+Note that intensity files only cache the written value and the actual
+change of hardware state occurs upon writing brightness file. This
+allows for changing many factors of the perceived color in a virtually
+unnoticeable way for the human observer.
+
+Multicolor Class Control
+========================
+The multicolor class presents the LED groups under a directory called "colors".
+This directory is a child 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 have two files created under the colors directory
+<color>_intensity and <color>_max_intensity. These files will contain
+one of LED_COLOR_ID_* definitions from the header
+include/dt-bindings/leds/common.h.
+
+Directory Layout Example
+========================
+root:/sys/class/leds/rgb:grouped_leds# ls -lR colors/
+-rw-rwxr-- 1 root root 4096 Jul 7 03:10 red_max_intensity
+--w--wx-w- 1 root root 4096 Jul 7 03:10 red_intensity
+-rw-rwxr-- 1 root root 4096 Jul 7 03:10 green_max_intensity
+--w--wx-w- 1 root root 4096 Jul 7 03:10 green_intensity
+-rw-rwxr-- 1 root root 4096 Jul 7 03:10 blue_max_intensity
+--w--wx-w- 1 root root 4096 Jul 7 03:10 blue_intensity
+
+Multicolor Class Brightness Control
+===================================
+The multiclor class framework will calculate each monochrome LEDs intensity.
+
+The brightness level for each LED is calculated based on the color LED
+intensity setting divided by the color LED max intensity setting multiplied by
+the requested brightness.
+
+led_brightness = brightness * <color>_intensity/<color>_max_intensity
+
+Example:
+Three LEDs are present in the group as defined in "Directory Layout Example"
+within this document.
+
+A user first writes the color LED brightness file with the brightness level that
+is necessary to achieve a blueish violet output from the RGB LED group.
+
+echo 138 > /sys/class/leds/rgb:grouped_leds/red_intensity
+echo 43 > /sys/class/leds/rgb:grouped_leds/green_intensity
+echo 226 > /sys/class/leds/rgb:grouped_leds/blue_intensity
+
+red -
+ intensity = 138
+ max_intensity = 255
+green -
+ intensity = 43
+ max_intensity = 255
+blue -
+ intensity = 226
+ max_intensity = 255
+
+The user can control the brightness of that RGB group by writing the parent
+'brightness' control. Assuming a parent 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
+parent brightness file then the values written to each LED will be adjusted
+base on this value
+
+cat /sys/class/leds/rgb:grouped_leds/max_brightness
+255
+echo 128 > /sys/class/leds/rgb:grouped_leds/brightness
+
+adjusted_red_value = 128 * 138/255 = 69
+adjusted_green_value = 128 * 43/255 = 21
+adjusted_blue_value = 128 * 226/255 = 113
+
+Reading the parent brightness file will return the current brightness value of
+the color LED group.
+
+cat /sys/class/leds/rgb:grouped_leds/max_brightness
+255
+
+echo 128 > /sys/class/leds/rgb:grouped_leds/brightness
+
+cat /sys/class/leds/rgb:grouped_leds/brightness
+128
--
2.22.0.214.g8dca754b1e
