[PATCH v4 07/12] leds: trigger: Enforce strict checks in led_trigger_is_hw_controlled()

With all existing triggers adopting the new interface, strict checks
could be enforced to make the semantics of hardware control triggers
clearer.

In detail, a hardware control trigger should:

- Implement offloaded() callback to indicate hardware control
- Associate with the LED classdev's hw_control_trigger string

Signed-off-by: Rong Zhang <[email protected]>
---
Changes in v3:
- New patch in the series, splitted from PATCH 3 (thanks Thomas
  Weißschuh)
---
 drivers/leds/led-triggers.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index de17a8bbb4d4..cb49a02a8b3c 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -42,9 +42,16 @@ static bool __led_trigger_is_hw_controlled(struct led_classdev *led_cdev)
 	if (!led_cdev->trigger)
 		return false;
 
+	if (!led_cdev->hw_control_trigger ||
+	    strcmp(led_cdev->hw_control_trigger, led_cdev->trigger->name))
+		return false;
+
 	if (led_cdev->trigger->offloaded)
 		return led_cdev->trigger->offloaded(led_cdev);
 
+	dev_warn_once(led_cdev->dev, "hw control trigger %s doesn't implement offloaded()\n",
+		      led_cdev->trigger->name);
+
 	/* Otherwise assume private triggers as always offloaded. */
 	return led_cdev->trigger->trigger_type;
 }

-- 
2.53.0