九、编写led驱动

led.c

 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/cdev.h>
 #include <linux/fs.h>
 #include <linux/io.h>

 #define GPMCON    0x7F008820
 #define GPMDAT    0x7F008824

 static int * __gp_gpmdat;

 static int led_open (struct inode *p_inode, struct file *p_file)
 {
     int *p_gpmcon = NULL;

     p_gpmcon = ioremap(GPMCON, );
     writel(0x1111, p_gpmcon);

     __gp_gpmdat = ioremap(GPMDAT, );

     return ;
 }

 static long led_ioctl (struct file *p_file, unsigned int cmd, unsigned long arg)
 {
     switch (cmd) {
     case :
         writel(0x0, __gp_gpmdat);
         break;

     case :
         writel(0xF, __gp_gpmdat);
         break;

     default:
         return -;
     }
     return ;
 }

 static struct cdev led_dev;
 static struct file_operations fops = {
     .open = led_open,
     .unlocked_ioctl = led_ioctl,
 };
 dev_t devno;

 static __init int led_init (void)
 {
     cdev_init(&led_dev, &fops);
     alloc_chrdev_region(&devno, , , "myled");
     cdev_add(&led_dev, devno, );

     return ;
 }

 static __exit void led_exit (void)
 {
     cdev_del(&led_dev);
     unregister_chrdev_region(devno, );
 }

 module_init(led_init);
 module_exit(led_exit);

 MODULE_LICENSE("GPL");

led_app.c

 #include <unistd.h>
 #include <sys/ioctl.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>

 int main(int argc, const char *argv[])
 {
     int fd, cmd;

     if (argc != ) {
         printf(".example: ./led_app 0\n");
         return;
     }

     cmd = atoi(argv[]);

     fd = open("/dev/myled", O_RDWR);

     ioctl(fd, cmd);

     return ;
 }

Makefile

 obj-m := led.o
 KDIR = /home/linux/zkf//urbetter-linux2.6.28-v1./

 all:
     make -C $(KDIR) $(objs) M=$(PWD) modules CROSS_COMPILE=arm-none-linux-gnueabi- ARCH=arm
     arm-none-linux-gnueabi-gcc led_app.c -o led_app
     sudo cp led.ko ~/zkf//rootfs/home/test
     sudo cp led_app ~/zkf//rootfs/home/test
 clean:
     rm *.o *.symvers *.mod.c *.order

　　make之后会生成led.ko和led_app两个要用到的文件，在Makefile中已经将他们复制到了开发板挂载目录中。在开发板终端中输入命令：insmod led.ko 之后输入命令：cat /proc/devices 可以看到myled主设备号为251

　　输入命令：mknod /dev/myled c 251 0

　　之后便能执行应用程序led_app了，执行 ./led_app 0 则点亮所有LED，执行 ./led_app 1 则熄灭所有LED。