学步园

linux2.6.32内核中LED类的构架已经完善，移植很简单，只用添加相关资源就可以了。

在mach-fz2440.c中添加相关头文件

/* for LEDS */
#include <linux/leds.h>

添加平台资源初始化文件

/* LED */
static struct gpio_led fz2440_leds[] = {
    [0] = {
        .name = "led1",
        .gpio = S3C2410_GPB(5),                                             //led对应gpio
        .active_low = 1,                                                              //低电平有效（点亮）
        .default_trigger = "heartbeat",                                        //默认触发
        .default_state = LEDS_GPIO_DEFSTATE_OFF,          //默认状态
    },
    [1] = {
        .name = "led2",
        .gpio = S3C2410_GPB(6),
        .active_low = 1,
        .default_trigger = "nand-disk",
        .default_state = LEDS_GPIO_DEFSTATE_OFF,
    },
    [2] = {
        .name = "led3",
        .gpio = S3C2410_GPB(7),
        .active_low = 1,
        .default_trigger = "default-on",
        .default_state = LEDS_GPIO_DEFSTATE_OFF,
    },
    [3] = {
        .name = "led4",
        .gpio = S3C2410_GPB(8),
        .active_low = 1,
        .default_trigger = "timer",
        .default_state = LEDS_GPIO_DEFSTATE_OFF,
    },
};
static struct gpio_led_platform_data s3c_gpio_led_pdata = {
    .num_leds = ARRAY_SIZE(fz2440_leds),
    .leds = fz2440_leds,
};
static struct platform_device s3c_device_led = {
    .name = "leds-gpio",
    .id   = -1,
    .dev  = {
               .platform_data = &s3c_gpio_led_pdata,
    },
};

static struct platform_device __initdata *fz2440_devices[] = {
&s3c_device_usb,
&s3c_device_lcd,
&s3c_device_wdt,
&s3c_device_i2c0,
&s3c_device_iis,
&s3c_device_nand,
&s3c_device_rtc,
&s3c_device_uda1341,
&s3c_device_adc,
&s3c_device_hwmon,
&s3c_device_ts,
&s3c_device_led,         //led平台设备文件
};

编译内核下载，看到"heartbeat"灯在闪烁，"default-on"等一直在亮着。

查看系统类设备

root@FZ:/sys/class/leds# ls
led1  led2  led3  led4

root@FZ:/sys/class/leds# cd led2
root@FZ:/sys/devices/platform/leds-gpio/leds/led2# ls
brightness      max_brightness  subsystem       uevent
device          power           trigger

让led2亮

root@FZ:/sys/devices/platform/leds-gpio/leds/led2# echo 1 > brightness

让led2灭

root@FZ:/sys/devices/platform/leds-gpio/leds/led2# echo 0 > brightness

写一个简单的应用测试程序

/*
 * leds.c - The first kernel app programming
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>

int main(int argc, char *argv[])
{
FILE *fp;
int led_no;
if(argc != 3)
{
printf("Usage: %s <led_no> <on/off>\n",argv[0]);
exit(0);
}
led_no = strtoul(argv[1],0,0);
switch (led_no)
{
case 2:
fp = fopen("/sys/class/leds/led2/brightness","w");
break;
case 3:
fp = fopen("/sys/class/leds/led3/brightness","w");
break;
case 4:
fp = fopen("/sys/class/leds/led4/brightness","w");
break;
default:
printf("err: no target led!\n");
break;
}
if(fp == NULL)
{
printf("err: cant open the file\n");
exit(0);
}
if(!strcmp(argv[2],"on")){
fputc('1',fp);
printf("led%d on!\n",led_no);
}else if(!strcmp(argv[2],"off")){
fputc('0',fp);
printf("led%d off!\n",led_no);
}
fclose(fp);
return 0;
}

编译

arm-linux-gcc -o leds leds.c

运行

./leds 3 on

看到led3点亮了