Hammer LED Class Driver

UserSpace Access
the LED onboard the hammer as well as the LED on the carrier board can be accessed from userspace via the sysfs interface. example interfaces are in /sys/devices/platform/s3c24xx_led.0/leds:led0/ and /sys/devices/platform/s3c24xx_led.1/leds:led1/. both directories include a file entry "brightness". to turn a LED on, echo a non zero value to the brightness file entry: echo 1 > /sys/devices/platform/s3c24xx_led.0/leds:led0/brightness to turn a LED off, echo a zero to the the brightness file entry: echo 0 > /sys/devices/platform/s3c24xx_led.0/leds:led0/brightness

you can also check the current status of the LED by using cat on the brightness file entry: cat /sys/devices/platform/s3c24xx_led.0/leds:led0/brightness

Adding New LEDS
a new LED connected via a GPIO can be defined in the linux-2.6.xx/arch/arm/mach-s3c2410/mach-tct_hammer.c file. each LED will need to include some platform data and a platform device definition:

static struct s3c24xx_led_platdata tct_hammer_pdata_led0 = { .gpio		= S3C2410_GPF0, .flags		= S3C24XX_LEDF_ACTLOW | S3C24XX_LEDF_TRISTATE, .name		= "led0", .def_trigger	= "timer", };

static struct platform_device tct_hammer_led0 = { .name		= "s3c24xx_led", .id		= 0, .dev		= { .platform_data = &tct_hammer_pdata_led0, }, };

this uses the standard LEDS class in the main kernel tree. for additional information see the linux-2.6.xx/Documentation/leds-class.txt file.

LED Hardware
the most common way of operating a LED via a gpio is to use an active low configuration: