Add hardware control support for the Netdev trigger.
The trigger on config change will check if the requested trigger can set
to blink mode using LED hardware mode and if every blink mode is supported,
the trigger will enable hardware mode with the requested configuration.
If there is at least one trigger that is not supported and can't run in
hardware mode, then software mode will be used instead.
A validation is done on every value change and on fail the old value is
restored and -EINVAL is returned.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/leds/trigger/ledtrig-netdev.c | 155 +++++++++++++++++++++++++-
 1 file changed, 149 insertions(+), 6 deletions(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index dd63cadb896e..ed019cb5867c 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c

@@ -37,6 +37,7 @@
  */
 
 struct led_netdev_data {
+	enum led_blink_modes blink_mode;
 	spinlock_t lock;
 
 	struct delayed_work work;

@@ -53,11 +54,105 @@ struct led_netdev_data {
 	bool carrier_link_up;
 };
 
+struct netdev_led_attr_detail {
+	char *name;
+	bool hardware_only;
+	enum led_trigger_netdev_modes bit;
+};
+
+static struct netdev_led_attr_detail attr_details[] = {
+	{ .name = "link", .bit = TRIGGER_NETDEV_LINK},
+	{ .name = "tx", .bit = TRIGGER_NETDEV_TX},
+	{ .name = "rx", .bit = TRIGGER_NETDEV_RX},
+};
+
+static bool validate_baseline_state(struct led_netdev_data *trigger_data)
+{
+	struct led_classdev *led_cdev = trigger_data->led_cdev;
+	struct netdev_led_attr_detail *detail;
+	u32 hw_blink_mode_supported = 0;
+	bool force_sw = false;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(attr_details); i++) {
+		detail = &attr_details[i];
+
+		/* Mode not active, skip */
+		if (!test_bit(detail->bit, &trigger_data->mode))
+			continue;
+
+		/* Hardware only mode enabled on software controlled led */
+		if (led_cdev->blink_mode == SOFTWARE_CONTROLLED &&
+		    detail->hardware_only)
+			return false;
+
+		/* Check if the mode supports hardware mode */
+		if (led_cdev->blink_mode != SOFTWARE_CONTROLLED) {
+			/* With a net dev set, force software mode.
+			 * With modes are handled by hardware, led will blink
+			 * based on his own events and will ignore any event
+			 * from the provided dev.
+			 */
+			if (trigger_data->net_dev) {
+				force_sw = true;
+				continue;
+			}
+
+			/* With empty dev, check if the mode is supported */
+			if (led_trigger_blink_mode_is_supported(led_cdev, detail->bit))
+				hw_blink_mode_supported |= BIT(detail->bit);
+		}
+	}
+
+	/* We can't run modes handled by both software and hardware.
+	 * Check if we run hardware modes and check if all the modes
+	 * can be handled by hardware.
+	 */
+	if (hw_blink_mode_supported && hw_blink_mode_supported != trigger_data->mode)
+		return false;
+
+	/* Modes are valid. Decide now the running mode to later
+	 * set the baseline.
+	 * Software mode is enforced with net_dev set. With an empty
+	 * one hardware mode is selected by default (if supported).
+	 */
+	if (force_sw || led_cdev->blink_mode == SOFTWARE_CONTROLLED)
+		trigger_data->blink_mode = SOFTWARE_CONTROLLED;
+	else
+		trigger_data->blink_mode = HARDWARE_CONTROLLED;
+
+	return true;
+}
+
 static void set_baseline_state(struct led_netdev_data *trigger_data)
 {
+	int i;
 	int current_brightness;
+	struct netdev_led_attr_detail *detail;
 	struct led_classdev *led_cdev = trigger_data->led_cdev;
 
+	/* Modes already validated. Directly apply hw trigger modes */
+	if (trigger_data->blink_mode == HARDWARE_CONTROLLED) {
+		/* We are refreshing the blink modes. Reset them */
+		led_cdev->hw_control_configure(led_cdev, BIT(TRIGGER_NETDEV_LINK),
+					       BLINK_MODE_ZERO);
+
+		for (i = 0; i < ARRAY_SIZE(attr_details); i++) {
+			detail = &attr_details[i];
+
+			if (!test_bit(detail->bit, &trigger_data->mode))
+				continue;
+
+			led_cdev->hw_control_configure(led_cdev, BIT(detail->bit),
+						       BLINK_MODE_ENABLE);
+		}
+
+		led_cdev->hw_control_start(led_cdev);
+
+		return;
+	}
+
+	/* Handle trigger modes by software */
 	current_brightness = led_cdev->brightness;
 	if (current_brightness)
 		led_cdev->blink_brightness = current_brightness;

@@ -100,10 +195,15 @@ static ssize_t device_name_store(struct device *dev,
 				 size_t size)
 {
 	struct led_netdev_data *trigger_data = led_trigger_get_drvdata(dev);
+	struct net_device *old_net = trigger_data->net_dev;
+	char old_device_name[IFNAMSIZ];
 
 	if (size >= IFNAMSIZ)
 		return -EINVAL;
 
+	/* Backup old device name */
+	memcpy(old_device_name, trigger_data->device_name, IFNAMSIZ);
+
 	cancel_delayed_work_sync(&trigger_data->work);
 
 	spin_lock_bh(&trigger_data->lock);

@@ -122,6 +222,19 @@ static ssize_t device_name_store(struct device *dev,
 		trigger_data->net_dev =
 		    dev_get_by_name(&init_net, trigger_data->device_name);
 
+	if (!validate_baseline_state(trigger_data)) {
+		/* Restore old net_dev and device_name */
+		if (trigger_data->net_dev)
+			dev_put(trigger_data->net_dev);
+
+		dev_hold(old_net);
+		trigger_data->net_dev = old_net;
+		memcpy(trigger_data->device_name, old_device_name, IFNAMSIZ);
+
+		spin_unlock_bh(&trigger_data->lock);
+		return -EINVAL;