Re: [PATCH v5 2/2] documention: leds: Add multicolor class documentation

From: Dan Murphy
Date: Tue Jul 16 2019 - 15:27:28 EST

Jacek

On 7/16/19 2:18 PM, Jacek Anaszewski wrote:
Hi Dan,

Thanks for the update. I have some nits below, please take a look.

On 7/1/19 10:46 PM, Dan Murphy wrote:
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@xxxxxx>
---
Documentation/leds/leds-class-multicolor.txt | 152 +++++++++++++++++++
1 file changed, 152 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..01175288502e
--- /dev/null
+++ b/Documentation/leds/leds-class-multicolor.txt
@@ -0,0 +1,152 @@
+
+Multi Color LED handling under Linux
+=================================================
+
+Author: Dan Murphy <dmurphy@xxxxxx>
+
+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 intensity 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 by the led_class
+framework. The led_class framework is documented in led-class.txt within this
+documentation directory.
+
+Each colored LED is given its own directory. These directories can be, but not
+limited to red, green, blue, white, amber, yellow and violet. Under these
+directories the intensity and max_intensity files are presented for each LED.
+
+
+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
+-rw------- 1 root root 4096 Jun 28 20:21 color_mix
+
+colors/blue:
+-rw------- 1 root root 4096 Jun 28 20:21 intensity
+-r-------- 1 root root 4096 Jun 28 20:27 max_intensity
+-r-------- 1 root root 4096 Jun 28 20:21 color_id
+
+colors/green:
+-rw------- 1 root root 4096 Jun 28 20:22 intensity
+-r-------- 1 root root 4096 Jun 28 20:27 max_intensity
+-r-------- 1 root root 4096 Jun 28 20:21 color_id
+
+colors/red:
+-rw------- 1 root root 4096 Jun 28 20:21 intensity
+-r-------- 1 root root 4096 Jun 28 20:27 max_intensity
+-r-------- 1 root root 4096 Jun 28 20:21 color_id
+
+Multicolor Color Mixing
+-----------------------
+Multicolor monochrome LEDs intensity can be modified and mixed to produce a
+varying array of colors. The color_mix file gives the user the ability to write
+all the monochrome LEDs registered in the directory with a single call.
+To create a specific color from monochrome LEDs the color_mix file needs to be
+written with each color's intensity. The order in which the monochrome LEDs
+should be written is based on the colors color_id.
+
+For example:
+cat /sys/class/leds/rgb:grouped_leds/red/color_id
+0
+cat /sys/class/leds/rgb:grouped_leds/green/color_id
+1
+cat /sys/class/leds/rgb:grouped_leds/blue/color_id
+2
+
+red - color_id = 0
+green - color_id = 1
+blue - color_id = 2
+
+These id's are the order in which to write the color_mix file.
+
+echo "<red> <green> <blue>" > color_mix
+
+echo "0x80 0x00 0x80" > color_mix
+
+The order of the monochrome LEDs are determined during multicolor class
+registration and will not change unless unregistered and re-registered.
+
+Other example with amber monochrome LED:
+blue - color_id = 0
+amber - color_id = 1
+
+In this exampe blue is at ID 0 and amber ID is 1 so the user would write
+echo "<blue> <amber>" > color_mix
+
+echo "0x38 0x80" > color_mix
+
+If a single monochrome LED needs to be modified then the user would write the
+colors/<color>/intensity file.
+
+
+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 value.
+
+led_brightness = requested_value*(led_color_intensity/led_color_max_intensity)
Please drop parentheses here as pointed out before in the code review.

Ack


+
+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 neccesary 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
We probably need to state here that any amendment to color intensity
values resets brightness to its max value.

Well that is not true. Intensity and brightness are two different spaces.

Brightness is for cluster control and intensity is for monochrome LED control.

There only relationship is when setting cluster brightness.


+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
Drop parentheses.

Ack

I have working code now. Just need to clean it up and test it.

Should be submitted by EOW.

Dan