leds: add camera LED triggers

Some LED devices support flash/torch functionality through the LED subsystem.
This patch enables direct LED trigger controls by the driver.
Flash on/off and torch on/off can be done simply by other driver space.
Two trigger APIs are added, ledtrig_flash_ctrl() and ledtrig_torch_ctrl().

Signed-off-by: Milo(Woogyom) Kim <[e-mail]>
Signed-off-by: Bryan Wu <[e-mail]>

drivers/leds/trigger/Kconfig

···
 	  GPIO/PWM based hardware.
 	  If unsure, say Y.
 
+config LEDS_TRIGGER_CAMERA
+	tristate "LED Camera Flash/Torch Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This allows LEDs to be controlled as a camera flash/torch device.
+	  This enables direct flash/torch on/off by the driver, kernel space.
+	  If unsure, say Y.
+
 endif # LEDS_TRIGGERS

drivers/leds/trigger/Makefile

···
 obj-$(CONFIG_LEDS_TRIGGER_CPU)		+= ledtrig-cpu.o
 obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o
 obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT)	+= ledtrig-transient.o
+obj-$(CONFIG_LEDS_TRIGGER_CAMERA)	+= ledtrig-camera.o

drivers/leds/trigger/ledtrig-camera.c

···
+/*
+ * Camera Flash and Torch On/Off Trigger
+ *
+ * based on ledtrig-ide-disk.c
+ *
+ * Copyright 2013 Texas Instruments
+ *
+ * Author: Milo(Woogyom) Kim <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+
+DEFINE_LED_TRIGGER(ledtrig_flash);
+DEFINE_LED_TRIGGER(ledtrig_torch);
+
+void ledtrig_flash_ctrl(bool on)
+{
+	enum led_brightness brt = on ? LED_FULL : LED_OFF;
+
+	led_trigger_event(ledtrig_flash, brt);
+}
+EXPORT_SYMBOL_GPL(ledtrig_flash_ctrl);
+
+void ledtrig_torch_ctrl(bool on)
+{
+	enum led_brightness brt = on ? LED_FULL : LED_OFF;
+
+	led_trigger_event(ledtrig_torch, brt);
+}
+EXPORT_SYMBOL_GPL(ledtrig_torch_ctrl);
+
+static int __init ledtrig_camera_init(void)
+{
+	led_trigger_register_simple("flash", &ledtrig_flash);
+	led_trigger_register_simple("torch", &ledtrig_torch);
+	return 0;
+}
+module_init(ledtrig_camera_init);
+
+static void __exit ledtrig_camera_exit(void)
+{
+	led_trigger_unregister_simple(ledtrig_torch);
+	led_trigger_unregister_simple(ledtrig_flash);
+}
+module_exit(ledtrig_camera_exit);
+
+MODULE_DESCRIPTION("LED Trigger for Camera Flash/Torch Control");
+MODULE_AUTHOR("Milo Kim");
+MODULE_LICENSE("GPL");

include/linux/leds.h

···
 static inline void ledtrig_ide_activity(void) {}
 #endif
 
+#if defined(CONFIG_LEDS_TRIGGER_CAMERA) || defined(CONFIG_LEDS_TRIGGER_CAMERA_MODULE)
+extern void ledtrig_flash_ctrl(bool on);
+extern void ledtrig_torch_ctrl(bool on);
+#else
+static inline void ledtrig_flash_ctrl(bool on) {}
+static inline void ledtrig_torch_ctrl(bool on) {}
+#endif
+
 /*
  * Generic LED platform data for describing LED names and default triggers.
  */