GPIO LEDS
How to use leds-gpio driver to manage states of connected leds of your Armadeus board.
Introduction
You can manage a led connected to a GPIO pin. The LED management is similar with the standard GPIO sysfs driver, but you have some new features like triggers (e.g. "heartbeat" LED blinks like a heart at the rate oh the CPU load) .
Configuration
First, you need to enable the leds-gpio driver in your kernel and some triggers like the "heartbeat" trigger to make the LED flash like a heartbeat.
Device Drivers --->
--- LED support
[*] LED Class Support
*** LED drivers ***
<*> LED Support for GPIO connected LEDs
[*] Platform device bindings for GPIO LEDs
*** LED Triggers ***
[*] LED Trigger support
<*> LED Timer Trigger
<*> LED Heartbeat Trigger
<*> LED backlight Trigger
<*> LED Default ON Trigger
Then, in your apf27-dev.c, you need to define your LED before the variable platform_devices[].
#include <linux/leds.h>
/* GPIO LED */
#if defined(CONFIG_LEDS_GPIO) || defined(CONFIG_LEDS_GPIO_MODULE)
static struct gpio_led apf27dev_led[] = {
{
.name = "apfdev:green:user",
.default_trigger = "heartbeat",
.gpio = (GPIO_PORTF | 14),
.active_low = 1,
},
};
static struct gpio_led_platform_data apf27dev_led_data = {
.num_leds = ARRAY_SIZE(apf27dev_led),
.leds = apf27dev_led
};
static struct platform_device apf27dev_led_dev = {
.name = "leds-gpio",
.id = -1,
.dev = {
.platform_data = &apf27dev_led_data,
},
};
#endif /* CONFIG_LEDS_GPIO */
Add the LED to get it managed by the kernel.
static struct platform_device *platform_devices[] __initdata = {
#if defined(CONFIG_LEDS_GPIO) || defined(CONFIG_LEDS_GPIO_MODULE)
&apf27dev_led_dev,
#endif
ALSA_SOUND
};
Then rebuild and update your bard with the new kernel. Upon the next kernel boot you should see the LED flash like a heartbeat (if you have activated the "heartbeat" trigger)
# ls /sys/class/leds/apfdev\:green\:user/ brightness max_brightness subsystem uevent device power trigger
You can change the trigger behaviors
# cat /sys/class/leds/apfdev\:green\:user/trigger [none] nand-disk timer heartbeat backlight gpio default-on # echo none > /sys/class/leds/apfdev\:green\:user/trigger
Switch on and off the LED
# cat /sys/class/leds/apfdev\:green\:user/max_brightness > /sys/class/leds/apfde v\:green\:user/brightness # echo 0 > /sys/class/leds/apfdev\:green\:user/brightness
