@@ -169,6 +169,28 @@ 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 offloading of LED triggers
+===================================
+
+Some LEDs can offload SW triggers to 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, both the trigger code and LED driver must support this.
+The LED must implement the trigger_offload() method and the trigger code must
+try to call this method (via led_trigger_offload() function) when configuration
+of the trigger (trigger_data) changes.
+
+The implementation of the trigger_offload() method by the LED driver must return
+0 if the offload is successful and -EOPNOTSUPP if the requested trigger
+configuration is not supported and the trigger should be executed in software.
+If trigger_offload() returns negative value, the trigger will be done in
+software, so any active offloading must also be disabled.
+
+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.
+
Known Issues
============
@@ -177,6 +177,7 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
flags);
cancel_work_sync(&led_cdev->set_brightness_work);
led_stop_software_blink(led_cdev);
+ led_trigger_offload_stop(led_cdev);
if (led_cdev->trigger->deactivate)
led_cdev->trigger->deactivate(led_cdev);
device_remove_groups(led_cdev->dev, led_cdev->trigger->groups);
@@ -148,6 +148,11 @@ struct led_classdev {
/* LEDs that have private triggers have this set */
struct led_hw_trigger_type *trigger_type;
+
+ /* some LEDs may be able to offload some SW triggers to HW */
+ int (*trigger_offload)(struct led_classdev *led_cdev,
+ bool enable);
+ bool offloaded;
#endif
#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
@@ -403,6 +408,30 @@ static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
return led_cdev->trigger_data;
}
+static inline int led_trigger_offload(struct led_classdev *led_cdev)
+{
+ int ret;
+
+ if (!led_cdev->trigger_offload)
+ return -EOPNOTSUPP;
+
+ ret = led_cdev->trigger_offload(led_cdev, true);
+ led_cdev->offloaded = !ret;
+
+ return ret;
+}
+
+static inline void led_trigger_offload_stop(struct led_classdev *led_cdev)
+{
+ if (!led_cdev->trigger_offload)
+ return;
+
+ if (led_cdev->offloaded) {
+ led_cdev->trigger_offload(led_cdev, false);
+ led_cdev->offloaded = false;
+ }
+}
+
/**
* led_trigger_rename_static - rename a trigger
* @name: the new trigger name
Add method trigger_offload() and member variable `offloaded` to struct led_classdev. Add helper functions led_trigger_offload() and led_trigger_offload_stop(). The trigger_offload() method, when implemented by the LED driver, should be called (via led_trigger_offload() function) from trigger code wanting to be offloaded at the moment when configuration of the trigger changes. If the trigger is successfully offloaded, this method returns 0 and the trigger does not have to blink the LED in software. If the trigger with given configuration cannot be offloaded, the method should return -EOPNOTSUPP, in which case the trigger must blink the LED in SW. The second argument to trigger_offload() being false means that the offloading is being disabled. In this case the function must return 0, errors are not permitted. Signed-off-by: Marek Behún <kabel@kernel.org> --- Documentation/leds/leds-class.rst | 22 ++++++++++++++++++++++ drivers/leds/led-triggers.c | 1 + include/linux/leds.h | 29 +++++++++++++++++++++++++++++ 3 files changed, 52 insertions(+)