字符设备实现控制led的驱动

zhanglong71

一个led驱动，做个记号

硬软件环境：s3c2440/linux-2.6.36/busybox-1.18.4/arm-linux-gcc 4.4.3

下面是模块c代码：

#include <linux/module.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/cdev.h> #include <asm/io.h> #include <asm/uaccess.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("zhanglong"); /*  * 板子上的led1,2,4,8分别对应连在GPF4,5,6,7上  *  *GPFCON ==> 0x56000050  *GPFDAT ==> 0x56000054  *GPFUP ==> 0x56000058  *  */ #define IO_PHYS 0x56000000 #define GPFCON_OFFSET   0x50 #define GPFDAT_OFFSET   0x54 #define GPFUP_OFFSET   0x58 struct led_device_s {     struct cdev dev;     dev_t  no;     short *io_gpfcon;   //注意数据类型, 前面因为错误声明为char型指针，造成结果与预期的不同，郁闷了很久.     char *io_gpfdat;     char *io_gpfup; }; struct led_device_s  my_led[4]; ssize_t my_write(struct file *fp, const char __user *buf, size_t count, loff_t *off) {     struct led_device_s *get = fp->private_data;     unsigned int    minor;     minor = MINOR(get->no);         *(get->io_gpfcon) &= ~(3 << ((minor * 2) + 8));     *(get->io_gpfcon) |= (1 << ((minor * 2) + 8));     *(get->io_gpfup) &= ~(1 << (minor + 4));     if((*buf == 0) || (*buf == 48)) {         *(get->io_gpfdat) &= ~(1 << (minor + 4));     } else {         *(get->io_gpfdat) |= (1 << (minor + 4));     }     return  4; } ssize_t my_read(struct file *fp, char __user *buf, size_t count, loff_t *off) {     return  4;  //不能返回0, 否则读相关设备时会卡住. } int my_open(struct inode *no, struct file *fp) {     fp->private_data = container_of(no->i_cdev, struct led_device_s, dev);     //printk(" kernel: open.\n");     return 0; } int my_release(struct inode *no, struct file *fp) {     //printk(" kernel: release.\n");     return 0; } struct file_operations my_ops = {     .open = my_open,     .release = my_release,     .read = my_read,     .write = my_write, }; int test_init(void) {     int ret = 0;     char *virt;     int i;        virt = ioremap(IO_PHYS, SZ_4K);     for (i = 0; i < 4; i ++) {         my_led[i].no = MKDEV(52, i);         cdev_init(&my_led[i].dev, &my_ops);         my_led[i].io_gpfcon = virt + GPFCON_OFFSET;         my_led[i].io_gpfdat = virt + GPFDAT_OFFSET;         my_led[i].io_gpfup = virt + GPFUP_OFFSET;     }     ret = register_chrdev_region(my_led[0].no, 4, "my dev");     if (ret) {         printk(" register device number failed.\n");         return ret;     }     for (i = 0; i < 4; i ++) {         cdev_add(&my_led[i].dev, my_led[i].no, 1);     }     return ret; } void test_exit(void) {     int i ;     for (i = 0; i < 4; i ++) {         cdev_del(&my_led[i].dev);     }     unregister_chrdev_region(my_led[0].no, 4);    } module_init(test_init); module_exit(test_exit);

下面是Makefile文件内容

#KERNEL    = /home/zl/my2440-2.6.13 KERNEL    = /media/STUDY/linux/kernel/my2440-2.6.36 #KERNEL    = /lib/modules/$(shell uname -r)/build default:     make -C $(KERNEL) M=$(shell pwd) modules clean:     make -C $(KERNEL) M=$(shell pwd) modules clean obj-m    += test.o

执行make命令后，“insmod test.ko”插入模块。用
echo 1 > led0_node
echo 0 > led0_node

echo 1 > led1_node
echo 0 > led1_node

echo 1 > led2_node
echo 0 > led2_node

echo 1 > led3_node
echo 0 > led3_node
即可使led灭或亮

其中led0_node,led1_node,led2_node,led3_node必须是字符设备文件，主，次设备号分别为(52,0)(52,1)(52,2)(52,3)

led0_node,led1_node,led2_node,led3_node对应的GPF4,5,6,7控制的led