arm 驱动基础：通过次设备号精确控制led亮灭
原理图：
驱动程序代码：
#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/delay.h>#include <asm/uaccess.h>#include <asm/irq.h>#include <asm/io.h>#include <asm/arch/regs-gpio.h>#include <asm/hardware.h>#define DEVICE_NAME "leds" /* 加载模式后，执行”cat /proc/devices”命令看到的设备名称 */#define LED_MAJOR 231 /* 主设备号 */static struct class *leds_class;static struct class_device *leds_class_devs[4];/* bit0<=>D10, 0:亮, 1:灭 * bit1<=>D11, 0:亮, 1:灭 * bit2<=>D12, 0:亮, 1:灭 */ static char leds_status = 0x0; static DECLARE_MUTEX(leds_lock); // 定义赋值//static int minor;static unsigned long gpio_va;#define GPIO_OFT(x) ((x) - 0x56000000)#define GPFCON (*(volatile unsigned long *)(gpio_va + GPIO_OFT(0x56000050)))#define GPFDAT (*(volatile unsigned long *)(gpio_va + GPIO_OFT(0x56000054)))/* 应用程序对设备文件/dev/leds执行open(...)时， * 就会调用s3c24xx_leds_open函数 */static int s3c24xx_leds_open(struct inode *inode, struct file *file){ int minor = MINOR(inode->i_rdev); //MINOR(inode->i_cdev); switch(minor) { case 0: /* /dev/leds */ { // 配置3引脚为输出 //s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP); GPFCON &= ~(0x3<<(4*2)); GPFCON |= (1<<(4*2)); //s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP); GPFCON &= ~(0x3<<(5*2)); GPFCON |= (1<<(5*2)); //s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP); GPFCON &= ~(0x3<<(6*2)); GPFCON |= (1<<(6*2)); // 都输出0 //s3c2410_gpio_setpin(S3C2410_GPF4, 0); GPFDAT &= ~(1<<4); //s3c2410_gpio_setpin(S3C2410_GPF5, 0); GPFDAT &= ~(1<<5); //s3c2410_gpio_setpin(S3C2410_GPF6, 0); GPFDAT &= ~(1<<6); down(&leds_lock); leds_status = 0x0; up(&leds_lock); break; } case 1: /* /dev/led1 */ { s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP); s3c2410_gpio_setpin(S3C2410_GPF4, 0); down(&leds_lock); leds_status &= ~(1<<0); up(&leds_lock); break; } case 2: /* /dev/led2 */ { s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP); s3c2410_gpio_setpin(S3C2410_GPF5, 0); leds_status &= ~(1<<1); break; } case 3: /* /dev/led3 */ { s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP); s3c2410_gpio_setpin(S3C2410_GPF6, 0); down(&leds_lock); leds_status &= ~(1<<2); up(&leds_lock); break; } } return 0;}static int s3c24xx_leds_read(struct *filp, char __user *buff, size_t count, loff_t *offp){ int minor = MINOR(filp->f_dentry->d_inode->i_rdev); char val; switch (minor) { case 0: /* /dev/leds */ { copy_to_user(buff, (const void *)&leds_status, 1); break; } case 1: /* /dev/led1 */ { down(&leds_lock); val = leds_status & 0x1; up(&leds_lock); copy_to_user(buff, (const void *)&val, 1); break; } case 2: /* /dev/led2 */ { down(&leds_lock); val = (leds_status>>1) & 0x1; up(&leds_lock); copy_to_user(buff, (const void *)&val, 1); break; } case 3: /* /dev/led3 */ { down(&leds_lock); val = (leds_status>>2) & 0x1; up(&leds_lock); copy_to_user(buff, (const void *)&val, 1); break; } } return 1;}static ssize_t s3c24xx_leds_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos){ //int minor = MINOR(inode->i_rdev); //MINOR(inode->i_cdev); int minor = MINOR(file->f_dentry->d_inode->i_rdev); char val; copy_from_user(&val, buf, 1); switch (minor) { case 0: /* /dev/leds */ { s3c2410_gpio_setpin(S3C2410_GPF4, (val & 0x1)); s3c2410_gpio_setpin(S3C2410_GPF5, (val & 0x1)); s3c2410_gpio_setpin(S3C2410_GPF6, (val & 0x1)); down(&leds_lock); leds_status = val; up(&leds_lock); break; } case 1: /* /dev/led1 */ { s3c2410_gpio_setpin(S3C2410_GPF4, val); if (val == 0) { down(&leds_lock); leds_status &= ~(1<<0); up(&leds_lock); } else { down(&leds_lock); leds_status |= (1<<0); up(&leds_lock); } break; } case 2: /* /dev/led2 */ { s3c2410_gpio_setpin(S3C2410_GPF5, val); if (val == 0) { down(&leds_lock); leds_status &= ~(1<<1); up(&leds_lock); } else { down(&leds_lock); leds_status |= (1<<1); up(&leds_lock); } break; } case 3: /* /dev/led3 */ { s3c2410_gpio_setpin(S3C2410_GPF6, val); if (val == 0) { down(&leds_lock); leds_status &= ~(1<<2); up(&leds_lock); } else { down(&leds_lock); leds_status |= (1<<2); up(&leds_lock); } break; } } return 1;}/* 这个结构是字符设备驱动程序的核心 * 当应用程序操作设备文件时所调用的open、read、write等函数， * 最终会调用这个结构中指定的对应函数 */static struct file_operations s3c24xx_leds_fops = { .owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */ .open = s3c24xx_leds_open, .read = s3c24xx_leds_read, .write = s3c24xx_leds_write, };/* * 执行insmod命令时就会调用这个函数 */static int __init s3c24xx_leds_init(void)//static int __init init_module(void){ int ret; int minor = 0; gpio_va = ioremap(0x56000000, 0x100000); if (!gpio_va) { return -EIO; } /* 注册字符设备 * 参数为主设备号、设备名字、file_operations结构； * 这样，主设备号就和具体的file_operations结构联系起来了， * 操作主设备为LED_MAJOR的设备文件时，就会调用s3c24xx_leds_fops中的相关成员函数 * LED_MAJOR可以设为0，表示由内核自动分配主设备号 */ ret = register_chrdev(LED_MAJOR, DEVICE_NAME, &s3c24xx_leds_fops); if (ret < 0) { printk(DEVICE_NAME " can't register major number\n"); return ret; } leds_class = class_create(THIS_MODULE, "leds"); if (IS_ERR(leds_class)) return PTR_ERR(leds_class); leds_class_devs[0] = class_device_create(leds_class, NULL, MKDEV(LED_MAJOR, 0), NULL, "leds"); for (minor = 1; minor < 4; minor++) { leds_class_devs[minor] = class_device_create(leds_class, NULL, MKDEV(LED_MAJOR, minor), NULL, "led%d", minor); if (unlikely(IS_ERR(leds_class_devs[minor]))) return PTR_ERR(leds_class_devs[minor]); } printk(DEVICE_NAME " initialized\n"); return 0;}/* * 执行rmmod命令时就会调用这个函数 */static void __exit s3c24xx_leds_exit(void){ int minor; /* 卸载驱动程序 */ unregister_chrdev(LED_MAJOR, DEVICE_NAME); for (minor = 0; minor < 4; minor++) { class_device_unregister(leds_class_devs[minor]); } class_destroy(leds_class); iounmap(gpio_va);}/* 这两行指定驱动程序的初始化函数和卸载函数 */module_init(s3c24xx_leds_init);module_exit(s3c24xx_leds_exit);/* 描述驱动程序的一些信息，不是必须的 */MODULE_AUTHOR("http://www.100ask.net");MODULE_VERSION("0.1.0");MODULE_DESCRIPTION("S3C2410/S3C2440 LED Driver");MODULE_LICENSE("GPL");
应用程序代码：
#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>/* * ledtest <dev> <on|off> */void print_usage(char *file){ printf("Usage:\n"); printf("%s <dev> <on|off>\n",file); printf("eg. \n"); printf("%s /dev/leds on\n", file); printf("%s /dev/leds off\n", file); printf("%s /dev/led1 on\n", file); printf("%s /dev/led1 off\n", file);}int main(int argc, char **argv){ int fd; char* filename; char val; if (argc != 3) { print_usage(argv[0]); return 0; } filename = argv[1]; fd = open(filename, O_RDWR); if (fd < 0) { printf("error, can't open %s\n", filename); return 0; } if (!strcmp("on", argv[2])) { // 亮灯 val = 0; write(fd, &val, 1); } else if (!strcmp("off", argv[2])) { // 灭灯 val = 1; write(fd, &val, 1); } else { print_usage(argv[0]); return 0; } return 0;}
