platform/x86: dell-laptop: Add micmute LED trigger support

This patch adds the LED trigger support for audio mic-mute control.
As of this patch, the LED device isn't tied with the audio driver, and
can be changed via user-space at "platform::micmute" sysfs entry.
(This new prefix "platform" is the agreement among people for
indicating the generic laptop / system-wide attribute.)

The binding with HD-audio is still done via the existing exported
dell_micmute_led_set().  It will be replaced with the LED trigger
binding in later patches.

Also this selects CONFIG_LEDS_TRIGGERS and CONFIG_LEDS_TRIGGERS_AUDIO
unconditionally.  Strictly speaking, these aren't 100% mandatory, but
leaving these manual selections would lead to a functional regression
easily once after converting from the dynamic symbol binding to the
LEDs trigger in a later patch.
Acked-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

drivers/platform/x86/Kconfig

@@ -177,6 +177,8 @@ config DELL_LAPTOP
 	select POWER_SUPPLY
 	select LEDS_CLASS
 	select NEW_LEDS
+	select LEDS_TRIGGERS
+	select LEDS_TRIGGER_AUDIO
 	---help---
 	This driver adds support for rfkill and backlight control to Dell
 	laptops (except for some models covered by the Compal driver).

drivers/platform/x86/dell-laptop.c

@@ -2131,6 +2131,23 @@ int dell_micmute_led_set(int state)
 }
 EXPORT_SYMBOL_GPL(dell_micmute_led_set);
 
+static int micmute_led_set(struct led_classdev *led_cdev,
+			   enum led_brightness brightness)
+{
+	int state = brightness != LED_OFF;
+	int err;
+
+	err = dell_micmute_led_set(state);
+	return err < 0 ? err : 0;
+}
+
+static struct led_classdev micmute_led_cdev = {
+	.name = "platform::micmute",
+	.max_brightness = 1,
+	.brightness_set_blocking = micmute_led_set,
+	.default_trigger = "audio-micmute",
+};
+
 static int __init dell_init(void)
 {
 	struct calling_interface_token *token;
@@ -2175,6 +2192,11 @@ static int __init dell_init(void)
 
 	dell_laptop_register_notifier(&dell_laptop_notifier);
 
+	micmute_led_cdev.brightness = ledtrig_audio_get(LED_AUDIO_MICMUTE);
+	ret = led_classdev_register(&platform_device->dev, &micmute_led_cdev);
+	if (ret < 0)
+		goto fail_led;
+
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		return 0;
 
@@ -2220,6 +2242,8 @@ static int __init dell_init(void)
 fail_get_brightness:
 	backlight_device_unregister(dell_backlight_device);
 fail_backlight:
+	led_classdev_unregister(&micmute_led_cdev);
+fail_led:
 	dell_cleanup_rfkill();
 fail_rfkill:
 	platform_device_del(platform_device);
@@ -2239,6 +2263,7 @@ static void __exit dell_exit(void)
 		touchpad_led_exit();
 	kbd_led_exit();
 	backlight_device_unregister(dell_backlight_device);
+	led_classdev_unregister(&micmute_led_cdev);
 	dell_cleanup_rfkill();
 	if (platform_device) {
 		platform_device_unregister(platform_device);