[RFC PATCH 2/6] leds: permit to declare supported offload triggers

[Ansuel Smith <ansuelsmth@gmail.com>]

With LEDs that can be offload driven, permit to declare supported triggers
in the dts and add them to the cled struct to be used by the related
offload trigger. This is particurally useful for phy that have support
for HW blinking on tx/rx traffic or based on the speed link.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 Documentation/leds/leds-class.rst |  4 ++++
 drivers/leds/led-class.c          | 15 ++++++++++++++-
 include/linux/leds.h              |  5 ++++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
index 035a738afc4a..ab50b58d6a21 100644
--- a/Documentation/leds/leds-class.rst
+++ b/Documentation/leds/leds-class.rst
@@ -191,6 +191,10 @@ If the second argument (enable) to the trigger_offload() method is false, any
 active HW offloading must be deactivated. In this case errors are not permitted
 in the trigger_offload() method.
 
+LEDs can declare the supported offload trigger using linux,supported-offload-triggers
+binding in the dts. This is just an array of string that will be used by any
+offload trigger to check the supported triggers and configure the LED offload mode
+and bheaviour.
 
 Known Issues
 ============
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index f4bb02f6e042..56f75e70b81e 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -339,7 +339,7 @@ int led_classdev_register_ext(struct device *parent,
 	char composed_name[LED_MAX_NAME_SIZE];
 	char final_name[LED_MAX_NAME_SIZE];
 	const char *proposed_name = composed_name;
-	int ret;
+	int count, ret;
 
 	if (init_data) {
 		if (init_data->devname_mandatory && !init_data->devicename) {
@@ -358,6 +358,19 @@ int led_classdev_register_ext(struct device *parent,
 			if (fwnode_property_present(init_data->fwnode,
 						    "retain-state-shutdown"))
 				led_cdev->flags |= LED_RETAIN_AT_SHUTDOWN;
+
+			if (fwnode_property_present(init_data->fwnode,
+						    "linux,supported-offload-triggers")) {
+				count = fwnode_property_string_array_count(
+				    init_data->fwnode, "linux,supported-offload-triggers");
+
+				led_cdev->supported_offload_triggers =
+				    kcalloc(count, sizeof(char *), GFP_KERNEL);
+				fwnode_property_read_string_array(
+				    init_data->fwnode, "linux,supported-offload-triggers",
+				    led_cdev->supported_offload_triggers, count);
+				led_cdev->supported_offload_triggers_count = count;
+			}
 		}
 	} else {
 		proposed_name = led_cdev->name;
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 949ab461287f..ff1f903f8079 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -157,7 +157,10 @@ struct led_classdev {
 
 #ifdef CONFIG_LEDS_OFFLOAD_TRIGGERS
 	int			offloaded;
-	/* some LEDs cne be driven by HW */
+	/* LEDs can have multiple offload triggers */
+	int			supported_offload_triggers_count;
+	const char		**supported_offload_triggers;
+	/* some LEDs may be able to offload some SW triggers to HW */
 	int			(*trigger_offload)(struct led_classdev *led_cdev,
 						   bool enable);
 #endif
-- 
2.32.0