leds: lp55xx: enable setting default trigger

This enables setting a default trigger on an LP55xx channel,
either from platform data or device tree. This mechanism is
identical to the mechanism for GPIO LEDs and references the
common LEDs device tree bindings.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Milo Kim <milo.kim@ti.com>
Acked-by: Milo Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

Documentation/devicetree/bindings/leds/leds-lp55xx.txt

@@ -17,12 +17,15 @@ Optional properties:
          2: D1~6 with VOUT, D7~9 with VDD
          3: D1~9 are connected to VOUT
 
-Alternatively, each child can have specific channel name
-- chan-name: Name of each channel name
+Alternatively, each child can have a specific channel name and trigger:
+- chan-name (optional): name of channel
+- linux,default-trigger (optional): see
+  Documentation/devicetree/bindings/leds/common.txt
 
 example 1) LP5521
 3 LED channels, external clock used. Channel names are 'lp5521_pri:channel0',
-'lp5521_pri:channel1' and 'lp5521_pri:channel2'
+'lp5521_pri:channel1' and 'lp5521_pri:channel2', with a heartbeat trigger
+on channel 0.
 
 lp5521@32 {
 	compatible = "national,lp5521";
@@ -33,6 +36,7 @@ lp5521@32 {
 	chan0 {
 		led-cur = /bits/ 8 <0x2f>;
 		max-cur = /bits/ 8 <0x5f>;
+		linux,default-trigger = "heartbeat";
 	};
 
 	chan1 {

drivers/leds/leds-lp55xx-common.c

@@ -165,6 +165,7 @@ static int lp55xx_init_led(struct lp55xx_led *led,
 	led->led_current = pdata->led_config[chan].led_current;
 	led->max_current = pdata->led_config[chan].max_current;
 	led->chan_nr = pdata->led_config[chan].chan_nr;
+	led->cdev.default_trigger = pdata->led_config[chan].default_trigger;
 
 	if (led->chan_nr >= max_channel) {
 		dev_err(dev, "Use channel numbers between 0 and %d\n",
@@ -586,6 +587,8 @@ int lp55xx_of_populate_pdata(struct device *dev, struct device_node *np)
 		of_property_read_string(child, "chan-name", &cfg[i].name);
 		of_property_read_u8(child, "led-cur", &cfg[i].led_current);
 		of_property_read_u8(child, "max-cur", &cfg[i].max_current);
+		cfg[i].default_trigger =
+			of_get_property(child, "linux,default-trigger", NULL);
 
 		i++;
 	}

include/linux/platform_data/leds-lp55xx.h

@@ -22,6 +22,7 @@
 
 struct lp55xx_led_config {
 	const char *name;
+	const char *default_trigger;
 	u8 chan_nr;
 	u8 led_current; /* mA x10, 0 if led is not connected */
 	u8 max_current;