On 11/8/21 6:26 PM, Ansuel Smith wrote:
diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
index cd155ead8703..645940b78d81 100644
--- a/Documentation/leds/leds-class.rst
+++ b/Documentation/leds/leds-class.rst
@@ -169,6 +169,34 @@ Setting the brightness to zero with brightness_set() callback function
should completely turn off the LED and cancel the previously programmed
hardware blinking function, if any.
+Hardware driven LEDs
+===================================
+
+Some LEDs can be driven by hardware (for example a LED connected to
+an ethernet PHY or an ethernet switch can be configured to blink on activity on
+the network, which in software is done by the netdev trigger).
+
+To do such offloading, LED driver must support this and a supported trigger must
+be used.
+
+LED driver should declare the correct blink_mode supported and should set the
+blink_mode parameter to one of HARDWARE_CONTROLLED or SOFTWARE_HARDWARE_CONTROLLED.
+The trigger will check this option and fail to activate if the blink_mode is not
+supported. By default if a LED driver doesn't declare blink_mode, SOFTWARE_CONTROLLED
+is assumed.
+
+The LED must implement 3 main API:
APIs:
+- hw_control_status(): This asks the LED driver if hardware mode is enabled
+ or not. Triggers will check if the hardware mode is active and will try
+ to offload their triggers if supported by the driver.
+- hw_control_start(): This will simply enable the hardware mode for the LED.
+- hw_control_stop(): This will simply disable the hardware mode for the LED.
+ It's advised to the driver to put the LED in the old state but this is not
for the driver
+ enforcerd and putting the LED off is also accepted.
enforced
+
+With HARDWARE_CONTROLLED blink_mode hw_control_status/start/stop is optional
+and any software only trigger will reject activation as the LED supports only
+hardware mode.
Known Issues
============
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index ed800f5da7d8..bd2b19cc77ec 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -49,6 +49,17 @@ config LEDS_BRIGHTNESS_HW_CHANGED
See Documentation/ABI/testing/sysfs-class-led for details.
+config LEDS_HARDWARE_CONTROL
+ bool "LED Hardware Control support"
+ help
+ This option enabled Hardware control support used by leds that
enables LEDs
+ can be driven in hardware by using supported triggers.
+
+ Hardware blink modes will be exposed by sysfs class in
+ /sys/class/leds based on the trigger currently active.
+
+ If unsure, say Y.
--
~Randy
