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Documentation: leds: Document pattern behavior of Samsung S2M series PMIC RGB LEDs

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Add documentation to describe how hardware patterns (as defined by the
documentation of leds-trigger-pattern) are parsed and implemented by the
Samsung S2M series PMIC RGB LED driver.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Link: https://patch.msgid.link/20260516-s2mu005-pmic-v7-8-73f9702fb461@disroot.org
Signed-off-by: Lee Jones <lee@kernel.org>
This commit is contained in:
Kaustabh Chakraborty
2026-05-16 03:08:40 +05:30
committed by Lee Jones
parent 63ccd117f4
commit 373777fb56
2 changed files with 61 additions and 0 deletions
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1
Documentation/leds/index.rst
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@@ -28,6 +28,7 @@ LEDs
leds-lp5812
leds-mlxcpld
leds-mt6370-rgb
leds-s2m-rgb
leds-sc27xx
leds-st1202
leds-qcom-lpg

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Documentation/leds/leds-s2m-rgb.rst Normal file
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@@ -0,0 +1,60 @@
.. SPDX-License-Identifier: GPL-2.0
======================================
Samsung S2M Series PMIC RGB LED Driver
======================================
Description
-----------
The RGB LED on the S2M series PMIC hardware features a three-channel LED that
is grouped together as a single device. Furthermore, it supports 8-bit
brightness control for each channel. This LED is typically used as a status
indicator in mobile devices. It also supports various parameters for hardware
patterns.
The hardware pattern can be programmed using the "pattern" trigger, using the
hw_pattern attribute.
/sys/class/leds/<led>/repeat
----------------------------
The hardware supports only indefinitely repeating patterns. The repeat
attribute must be set to -1 for hardware patterns to function.
/sys/class/leds/<led>/hw_pattern
--------------------------------
Specify a hardware pattern for the RGB LEDs.
The pattern is a series of brightness levels and durations in milliseconds.
There should be only one non-zero brightness level. Unlike the results
described in leds-trigger-pattern, the transitions between on and off states
are smoothed out by the hardware.
Simple pattern::
"255 3000 0 1000"
255 -+ ''''''-. .-'''''''-.
| '. .' '.
| \ / \
| '. .' '.
| '-.......-' '-
0 -+-------+-------+-------+-------+-------+-------+--> time (s)
0 1 2 3 4 5 6
As described in leds-trigger-pattern, it is also possible to use zero-length
entries to disable the ramping mechanism.
On-Off pattern::
"255 1000 255 0 0 1000 0 0"
255 -+ ------+ +-------+ +-------+
| | | | | |
| | | | | |
| | | | | |
| +-------+ +-------+ +-------
0 -+-------+-------+-------+-------+-------+-------+--> time (s)
0 1 2 3 4 5 6