leds: trigger: netdev: add support for LED hw control

Add support for LED hw control for the netdev trigger.

The trigger on calling set_baseline_state to configure a new mode, will
do various check to verify if hw control can be used for the requested
mode in can_hw_control() function.

It will first check if the LED driver supports hw control for the netdev
trigger, then will use hw_control_is_supported() and finally will call
hw_control_set() to apply the requested mode.

To use such mode, interval MUST be set to the default value and net_dev
MUST be set. If one of these 2 value are not valid, hw control will
never be used and normal software fallback is used.

The default interval value is moved to a define to make sure they are
always synced.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/leds/trigger/ledtrig-netdev.c

@@ -24,6 +24,8 @@
 #include <linux/timer.h>
 #include "../leds.h"
 
+#define NETDEV_LED_DEFAULT_INTERVAL	50
+
 /*
  * Configurable sysfs attributes:
  *
@@ -68,6 +70,13 @@ static void set_baseline_state(struct led_netdev_data *trigger_data)
 	int current_brightness;
 	struct led_classdev *led_cdev = trigger_data->led_cdev;
 
+	/* Already validated, hw control is possible with the requested mode */
+	if (trigger_data->hw_control) {
+		led_cdev->hw_control_set(led_cdev, trigger_data->mode);
+
+		return;
+	}
+
 	current_brightness = led_cdev->brightness;
 	if (current_brightness)
 		led_cdev->blink_brightness = current_brightness;
@@ -103,12 +112,42 @@ static bool supports_hw_control(struct led_classdev *led_cdev)
 
 static bool can_hw_control(struct led_netdev_data *trigger_data)
 {
+	unsigned long default_interval = msecs_to_jiffies(NETDEV_LED_DEFAULT_INTERVAL);
+	unsigned int interval = atomic_read(&trigger_data->interval);
 	struct led_classdev *led_cdev = trigger_data->led_cdev;
+	int ret;
 
 	if (!supports_hw_control(led_cdev))
 		return false;
 
-	return false;
+	/*
+	 * Interval must be set to the default
+	 * value. Any different value is rejected if in hw
+	 * control.
+	 */
+	if (interval != default_interval)
+		return false;
+
+	/*
+	 * net_dev must be set with hw control, otherwise no
+	 * blinking can be happening and there is nothing to
+	 * offloaded.
+	 */
+	if (!trigger_data->net_dev)
+		return false;
+
+	/* Check if the requested mode is supported */
+	ret = led_cdev->hw_control_is_supported(led_cdev, trigger_data->mode);
+	/* Fall back to software blinking if not supported */
+	if (ret == -EOPNOTSUPP)
+		return false;
+	if (ret) {
+		dev_warn(led_cdev->dev,
+			 "Current mode check failed with error %d\n", ret);
+		return false;
+	}
+
+	return true;
 }
 
 static ssize_t device_name_show(struct device *dev,
@@ -413,7 +452,7 @@ static int netdev_trig_activate(struct led_classdev *led_cdev)
 	trigger_data->device_name[0] = 0;
 
 	trigger_data->mode = 0;
-	atomic_set(&trigger_data->interval, msecs_to_jiffies(50));
+	atomic_set(&trigger_data->interval, msecs_to_jiffies(NETDEV_LED_DEFAULT_INTERVAL));
 	trigger_data->last_activity = 0;
 
 	led_set_trigger_data(led_cdev, trigger_data);