platform/x86: dell-*: Call new led hw_changed API on kbd brightness change

Make dell-wmi notify on hotkey kbd brightness changes, listen for this
in dell-laptop and call led_classdev_notify_brightness_hw_changed.

This will allow userspace to monitor (poll) for brightness changes on
these LEDs caused by the hotkey.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/dell-laptop.c

@@ -1984,6 +1984,7 @@ static int kbd_led_level_set(struct led_classdev *led_cdev,
 
 static struct led_classdev kbd_led = {
 	.name           = "dell::kbd_backlight",
+	.flags		= LED_BRIGHT_HW_CHANGED,
 	.brightness_set_blocking = kbd_led_level_set,
 	.brightness_get = kbd_led_level_get,
 	.groups         = kbd_led_groups,
@@ -1991,6 +1992,8 @@ static struct led_classdev kbd_led = {
 
 static int __init kbd_led_init(struct device *dev)
 {
+	int ret;
+
 	kbd_init();
 	if (!kbd_led_present)
 		return -ENODEV;
@@ -2002,7 +2005,11 @@ static int __init kbd_led_init(struct device *dev)
 		if (kbd_led.max_brightness)
 			kbd_led.max_brightness--;
 	}
-	return led_classdev_register(dev, &kbd_led);
+	ret = led_classdev_register(dev, &kbd_led);
+	if (ret)
+		kbd_led_present = false;
+
+	return ret;
 }
 
 static void brightness_set_exit(struct led_classdev *led_cdev,
@@ -2019,6 +2026,26 @@ static void kbd_led_exit(void)
 	led_classdev_unregister(&kbd_led);
 }
 
+static int dell_laptop_notifier_call(struct notifier_block *nb,
+				     unsigned long action, void *data)
+{
+	switch (action) {
+	case DELL_LAPTOP_KBD_BACKLIGHT_BRIGHTNESS_CHANGED:
+		if (!kbd_led_present)
+			break;
+
+		led_classdev_notify_brightness_hw_changed(&kbd_led,
+						kbd_led_level_get(&kbd_led));
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block dell_laptop_notifier = {
+	.notifier_call = dell_laptop_notifier_call,
+};
+
 static int __init dell_init(void)
 {
 	struct calling_interface_buffer *buffer;
@@ -2062,6 +2089,8 @@ static int __init dell_init(void)
 		debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL,
 				    &dell_debugfs_fops);
 
+	dell_laptop_register_notifier(&dell_laptop_notifier);
+
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		return 0;
 
@@ -2113,6 +2142,7 @@ static int __init dell_init(void)
 
 static void __exit dell_exit(void)
 {
+	dell_laptop_unregister_notifier(&dell_laptop_notifier);
 	debugfs_remove_recursive(dell_laptop_dir);
 	if (quirks && quirks->touchpad_led)
 		touchpad_led_exit();

drivers/platform/x86/dell-wmi.c

@@ -329,6 +329,10 @@ static void dell_wmi_process_key(int type, int code)
 	if (type == 0x0000 && code == 0xe025 && !wmi_requires_smbios_request)
 		return;
 
+	if (key->keycode == KEY_KBDILLUMTOGGLE)
+		dell_laptop_call_notifier(
+			DELL_LAPTOP_KBD_BACKLIGHT_BRIGHTNESS_CHANGED, NULL);
+
 	sparse_keymap_report_entry(dell_wmi_input_dev, key, 1, true);
 }