Re: [PATCH v21 02/16] leds: multicolor: Introduce a multicolor class definition
From: Jacek Anaszewski
Date: Tue Apr 28 2020 - 16:48:55 EST
Dan,
Thanks for the update.
On 4/28/20 6:03 PM, Dan Murphy wrote:
Introduce a multicolor class that groups colored LEDs
within a LED node.
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 the intensity file and the latter is controlled
via brightness file.
Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
---
.../ABI/testing/sysfs-class-led-multicolor | 34 +++
Documentation/leds/index.rst | 1 +
Documentation/leds/leds-class-multicolor.rst | 88 ++++++++
MAINTAINERS | 8 +
drivers/leds/Kconfig | 10 +
drivers/leds/Makefile | 1 +
drivers/leds/led-class-multicolor.c | 210 ++++++++++++++++++
include/linux/led-class-multicolor.h | 121 ++++++++++
8 files changed, 473 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-class-led-multicolor
create mode 100644 Documentation/leds/leds-class-multicolor.rst
create mode 100644 drivers/leds/led-class-multicolor.c
create mode 100644 include/linux/led-class-multicolor.h
diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
new file mode 100644
index 000000000000..7d33a82a4b07
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
@@ -0,0 +1,34 @@
+What: /sys/class/leds/<led>/brightness
+Date: March 2020
+KernelVersion: 5.8
+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 for each grouped LED via the
+ equation below:
+
+ led_brightness = brightness * multi_intensity/max_brightness
+
+ 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>/multi_index
+Date: March 2020
+KernelVersion: 5.8
+Contact: Dan Murphy <dmurphy@xxxxxx>
+Description: read
+ The multi_index array, when read, will output the LED colors
+ by name as they are indexed in the multi_intensity file.
+
+What: /sys/class/leds/<led>/multi_intensity
+Date: March 2020
+KernelVersion: 5.8
+Contact: Dan Murphy <dmurphy@xxxxxx>
+Description: read/write
+ Intensity level for the LED color within the array.
+ The intensities for each color must be entered based on the
+ multi_index array.
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..7e4907a5c87b
--- /dev/null
+++ b/Documentation/leds/leds-class-multicolor.rst
@@ -0,0 +1,88 @@
+====================================
+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.
+
+The num_multi_leds file returns the total number of LEDs that are presented in
+each multi_* array.
It is no longer present in this version.
+
+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 multi_index
+-rw-r--r-- 1 root root 4096 Oct 19 16:16 multi_intensity
What about max_brightness?
+
+Multicolor Class Brightness Control
+===================================
+The multicolor 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 parent max_brightness setting multiplied by
Parent is counter-intuitive in this case. I'd call it global.
+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
+parent 'brightness' control. Assuming a max_brightness of 255 the user
s/parent/global/
+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
Ditto.
+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 parent brightness file will return the current brightness value of
Ditto.
--
Best regards,
Jacek Anaszewski