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

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>

diff --git a/Documentation/leds/index.rst b/Documentation/leds/index.rst
index bebf440042787a0bb58907cfa88ef2210cc5bd60..23fa9ff7aaf4b0a287b4bb266b8d252112799cc6 100644 (file)
--- a/Documentation/leds/index.rst
+++ b/Documentation/leds/index.rst
@@ -28,6 +28,7 @@ LEDs
    leds-lp5812
    leds-mlxcpld
    leds-mt6370-rgb
+   leds-s2m-rgb
    leds-sc27xx
    leds-st1202
    leds-qcom-lpg

diff --git a/Documentation/leds/leds-s2m-rgb.rst b/Documentation/leds/leds-s2m-rgb.rst
new file mode 100644 (file)
index 0000000..4f89a8c
--- /dev/null
+++ b/Documentation/leds/leds-s2m-rgb.rst
@@ -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