[PATCH v5 2/6] leds: triggers: Add a keyboard backlight trigger

[Hans de Goede <hdegoede@redhat.com>]

Add a trigger to control keyboard backlight LED devices. Note that in
some cases the keyboard backlight control is hardwired (taken care of
in firmware outside of the kernels control), in that case this triggers
main purpose is to allow userspace to monitor these changes.

The ledtrig_kbd_backlight function has a set_brightness parameter to
differentiate between full backlight control through the trigger
(set_brightness set to true) or change notification only (false).

Note the Kconfig option for this is a bool because the code is so
small that it is not worth the overhead of being a module.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v5:
-This is a new patch in v5 of this patch-set (replacing earlier attempts
 at similar functionality)
---
 drivers/leds/trigger/Kconfig                 | 10 ++++++++
 drivers/leds/trigger/Makefile                |  1 +
 drivers/leds/trigger/ledtrig-kbd-backlight.c | 38 ++++++++++++++++++++++++++++
 include/linux/leds.h                         |  8 ++++++
 4 files changed, 57 insertions(+)
 create mode 100644 drivers/leds/trigger/ledtrig-kbd-backlight.c

diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
index 3f9ddb9..350e2c7 100644
--- a/drivers/leds/trigger/Kconfig
+++ b/drivers/leds/trigger/Kconfig
@@ -67,6 +67,16 @@ config LEDS_TRIGGER_BACKLIGHT
 
 	  If unsure, say N.
 
+config LEDS_TRIGGER_KBD_BACKLIGHT
+	bool "LED keyboard backlight Trigger"
+	depends on LEDS_TRIGGERS
+	help
+	  This trigger can control keyboard backlight LED devices,
+	  it also allows user-space to monitor keyboard backlight brightness
+	  changes done through e.g. hotkeys on some laptops.
+
+	  If unsure, say Y.
+
 config LEDS_TRIGGER_CPU
 	bool "LED CPU Trigger"
 	depends on LEDS_TRIGGERS
diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
index a72c43c..be6b249 100644
--- a/drivers/leds/trigger/Makefile
+++ b/drivers/leds/trigger/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_LEDS_TRIGGER_DISK)		+= ledtrig-disk.o
 obj-$(CONFIG_LEDS_TRIGGER_MTD)		+= ledtrig-mtd.o
 obj-$(CONFIG_LEDS_TRIGGER_HEARTBEAT)	+= ledtrig-heartbeat.o
 obj-$(CONFIG_LEDS_TRIGGER_BACKLIGHT)	+= ledtrig-backlight.o
+obj-$(CONFIG_LEDS_TRIGGER_KBD_BACKLIGHT) += ledtrig-kbd-backlight.o
 obj-$(CONFIG_LEDS_TRIGGER_GPIO)		+= ledtrig-gpio.o
 obj-$(CONFIG_LEDS_TRIGGER_CPU)		+= ledtrig-cpu.o
 obj-$(CONFIG_LEDS_TRIGGER_DEFAULT_ON)	+= ledtrig-default-on.o
diff --git a/drivers/leds/trigger/ledtrig-kbd-backlight.c b/drivers/leds/trigger/ledtrig-kbd-backlight.c
new file mode 100644
index 0000000..353ee92
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-kbd-backlight.c
@@ -0,0 +1,38 @@
+/*
+ * LED Trigger for keyboard backlight control
+ *
+ * Copyright 2016, Hans de Goede <hdegoede@redhat.com>
+ *
+ * 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/device.h>
+#include <linux/leds.h>
+#include "../leds.h"
+
+static struct led_trigger kbd_backlight_trigger = {
+	.name     = "kbd-backlight",
+	.activate = led_trigger_add_current_brightness,
+	.deactivate = led_trigger_remove_current_brightness,
+};
+
+void ledtrig_kbd_backlight(bool set_brightness, enum led_brightness brightness)
+{
+	if (set_brightness)
+		led_trigger_event(&kbd_backlight_trigger, brightness);
+
+	led_trigger_notify_current_brightness_change(&kbd_backlight_trigger);
+}
+EXPORT_SYMBOL_GPL(ledtrig_kbd_backlight);
+
+static int __init kbd_backlight_trig_init(void)
+{
+	return led_trigger_register(&kbd_backlight_trigger);
+}
+device_initcall(kbd_backlight_trig_init);
diff --git a/include/linux/leds.h b/include/linux/leds.h
index d3eb992..870b8c2 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -353,6 +353,14 @@ static inline void ledtrig_flash_ctrl(bool on) {}
 static inline void ledtrig_torch_ctrl(bool on) {}
 #endif
 
+#ifdef CONFIG_LEDS_TRIGGER_KBD_BACKLIGHT
+extern void ledtrig_kbd_backlight(bool set_brightness,
+				  enum led_brightness brightness);
+#else
+static inline void ledtrig_kbd_backlight(bool set_brightness,
+					 enum led_brightness brightness) {}
+#endif
+
 /*
  * Generic LED platform data for describing LED names and default triggers.
  */
-- 
2.9.3