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Subject[RFC PATCH 3/5] documention: leds: Add multicolor class documentation
Date
Add the support documentation on the multicolor LED framework.
This document defines the directores and file generated by the
multicolor framework. It also documents usage.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
---
Documentation/leds/leds-class-multicolor.txt | 99 ++++++++++++++++++++
1 file changed, 99 insertions(+)
create mode 100644 Documentation/leds/leds-class-multicolor.txt

diff --git a/Documentation/leds/leds-class-multicolor.txt b/Documentation/leds/leds-class-multicolor.txt
new file mode 100644
index 000000000000..8112b99a7668
--- /dev/null
+++ b/Documentation/leds/leds-class-multicolor.txt
@@ -0,0 +1,99 @@
+
+Multi Color LED handling under Linux
+=================================================
+
+Authors: Dan Murphy <dmurphy@ti.com>
+
+Description
+-----------
+There are varying monochrome LED colors available for application. These
+LEDs can be used as a single use case LED or can be mixed with other color
+LEDs to produce the full spectrum of color. Color LEDs that are grouped
+can be presented under a single LED node with individual color control.
+The multicolor class groups these LEDs and allows dynamically setting the value
+of a single LED or setting the brightness values of the LEDs in the group and
+updating the LEDs virtually simultaneously.
+
+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 but the led_class
+framework. The led_class framework is documented in led-class.txt within this
+documentation directory.
+
+Each colored LED is given it's own directory. These directories can be but not
+limited to red, green, blue, white, amber, yellow and violet. Under these
+directories the brightness and max_brightness files are presented for each LED.
+
+Under the "colors" directory there are two files created "sync" and
+"sync_enable". The sync_enable file controls whether the LED brightness
+value is set real time or if the LED brightness value setting is deferred until
+the "sync" file is written. If sync_enable is set then writing to each LED
+"brightness" file will store the brightness value. Once the "sync" file is
+written then each LED color defined in the node will write the brightness of
+the LED in the device driver.
+
+If "sync_enable" is not set then writing the brightness value of the LED to the
+device driver is done immediately. Writing the "sync" file has no affect.
+
+Directory Layout Example
+------------------------
+root:/sys/class/leds/rgb:grouped_leds# ls -lR colors/
+colors/:
+drwxr-xr-x 2 root root 0 Jun 28 20:21 blue
+drwxr-xr-x 2 root root 0 Jun 28 20:21 green
+drwxr-xr-x 2 root root 0 Jun 28 20:21 red
+--w------- 1 root root 4096 Jun 28 20:21 sync
+-rw------- 1 root root 4096 Jun 28 20:22 sync_enable
+
+colors/blue:
+-rw------- 1 root root 4096 Jun 28 20:21 brightness
+-r-------- 1 root root 4096 Jun 28 20:27 max_brightness
+
+colors/green:
+-rw------- 1 root root 4096 Jun 28 20:22 brightness
+-r-------- 1 root root 4096 Jun 28 20:27 max_brightness
+
+colors/red:
+-rw------- 1 root root 4096 Jun 28 20:21 brightness
+-r-------- 1 root root 4096 Jun 28 20:27 max_brightness
+
+Example of Writing LEDs with Sync Enabled
+-----------------------------------------
+Below the red, green and blue LEDs are set to corresponding values. These
+values are stored and not written until the sync file is written.
+
+cd /sys/class/leds/rgb:grouped_leds/colors
+
+echo 1 > sync_enable
+
+echo 100 > red/brightness
+echo 80 > green/brightness
+echo 180 > blue/brightness
+
+* LED device driver has not been updated and the LED states have not changed.
+* Writing the LED brightness files again will only change the stored value and
+* not the device driver value.
+
+echo 1 > sync
+
+* LED device driver has been updated the LEDs should present the brightness
+* levels that have been set. Since sync_enable is still enabled writing to the
+* LED brightness files will not change the current brightnesses.
+
+Example of Writing LEDs with Sync Disabled
+------------------------------------------
+Below the values of each LED are written to the device driver immediately upon
+request.
+
+cd /sys/class/leds/rgb:grouped_leds/colors
+
+echo 0 > sync_enable
+
+echo 100 > red/brightness // Red LED should be on with the current brightness
+echo 80 > green/brightness // Green LED should be on with the current brightness
+echo 180 > blue/brightness // Blue LED should be on with the current brightness
+.
+.
+.
+echo 0 > green/brightness // Green LED should be off
--
2.19.0
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