[PATCH RFC v2 1/9] leds: Add callback offloaded() to query the state of hardware control trigger

[Rong Zhang]

There are multiple triggers implementing hardware control. However, the
LED core doesn't really know the hardware control state since the
coordination is done directly between the trigger and the LED device.

Add an offloaded() callback so that the LED core can query the hardware
control state.

Signed-off-by: Rong Zhang <i@xxxxxxxx>
---
 Documentation/leds/leds-class.rst | 5 +++++
 include/linux/leds.h              | 1 +
 2 files changed, 6 insertions(+)

diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
index 5db620ed27aa..84665200a88d 100644
--- a/Documentation/leds/leds-class.rst
+++ b/Documentation/leds/leds-class.rst
@@ -235,6 +235,11 @@ LED driver must implement the following API to support hw control:
                 Returns a pointer to a struct device or NULL if nothing
                 is currently attached.
 
+LED trigger must implement the following API to support hw control:
+    - offloaded:
+                return a boolean indicating if the trigger is offloaded to
+                hardware.
+
 LED driver can activate additional modes by default to workaround the
 impossibility of supporting each different mode on the supported trigger.
 Examples are hardcoding the blink speed to a set interval, enable special
diff --git a/include/linux/leds.h b/include/linux/leds.h
index b16b803cc1ac..7332034a43c8 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -485,6 +485,7 @@ struct led_trigger {
 	const char	 *name;
 	int		(*activate)(struct led_classdev *led_cdev);
 	void		(*deactivate)(struct led_classdev *led_cdev);
+	bool		(*offloaded)(struct led_classdev *led_cdev);
 
 	/* Brightness set by led_trigger_event */
 	enum led_brightness brightness;

-- 
2.53.0