用内核定时器来实现的按键驱动代码分析以及测试代码
驱动代码：
#include <linux/errno.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/input.h> #include <linux/init.h> #include <linux/serio.h> #include <linux/delay.h> #include <linux/clk.h> #include <linux/wait.h> #include <linux/sched.h> #include <asm/io.h> #include <asm/irq.h> #include <asm/uaccess.h> #include <mach/regs-clock.h> #include <plat/regs-timer.h> #include <mach/regs-gpio.h> #include <linux/cdev.h> #include <linux/miscdevice.h> #include <linux/gpio.h> #include <asm-generic/poll.h> #include <linux/poll.h> #include <linux/device.h>//udev struct class *key_class; static int key_major = 0; struct key_desc_t { int pin; //which gpio pin int pin_dir;//input or output int number; char *name; }; /*设备结构体*/ static struct key_dev { struct cdev cdev; struct timer_list key_timer;/*内核定时器*/ }; struct key_dev *key_devp;//设备结构体指针 #define MAX_KEYS 5 /* 用来指定按键所用gpio的编号,方向和名字 */ static struct key_desc_t key_desc [] = { {S5PV210_GPH0(3), S3C_GPIO_INPUT, 0, "KEY1"}, /* K1 */ {S5PV210_GPH0(4), S3C_GPIO_INPUT, 1, "KEY2"}, /* K2 */ {S5PV210_GPH0(5), S3C_GPIO_INPUT, 2, "KEY3"}, /* K3 */ {S5PV210_GPH0(6), S3C_GPIO_INPUT, 3, "KEY4"}, /* K4 */ {S5PV210_GPH0(7), S3C_GPIO_INPUT, 4, "KEY5"}, /* K5 */ }; /* 按键被按下的次数*/ static volatile int key_values [MAX_KEYS] = {0, 0, 0, 0, 0}; /* 等待队列: * 当没有按键被按下时，如果有进程调用key_read函数， * 它将休眠 */ static DECLARE_WAIT_QUEUE_HEAD(key_waitq); #define KEY_TIMER_DELAY HZ/50 /*20ms*/ /* 事件标志, 有键按下时将它置1，key_read将它清0 */ static volatile int ev_press = 0; static void key_timer_handle(unsigned long data) { struct key_desc_t *key_p = (struct key_desc_t *)data; int down; static unsigned char pressed[MAX_KEYS] = {0}; int i; for(i=0;i<MAX_KEYS;i ++,key_p ++) { down = gpio_get_value(key_p->pin); if(!down) //key pressed { pressed[i] ++; if(pressed[i] > 2) pressed[i] = 3; } if((!down) && (2 == pressed[i]))//要等待20ms再检查一下该按键确实是被按下,而不是抖动 { printk("pressed\n"); key_values[i] = i + 1; ev_press = 1; /* 表示按键被按下了 */ wake_up_interruptible(&key_waitq); /* 唤醒休眠的进程 */ } if(down && pressed[i]) //如果该键被释放 { pressed[i] = 0; } } /*调度定时器再次执行*/ key_devp->key_timer.expires = jiffies + KEY_TIMER_DELAY; add_timer(&key_devp->key_timer); } /* 应用程序对设备文件/dev/key执行open(...)时， * 就会调用key_open函数 */ static int key_open(struct inode *inode, struct file *file) { return 0; } /* 应用程序对设备文件/dev/key执行close(...)时， * 就会调用key_close函数 */ static int key_close(struct inode *inode, struct file *file) { int i=0; for(i=0;i<MAX_KEYS;i++) gpio_free(key_desc[i].pin); return 0; } /* 应用程序对设备文件/dev/key执行read(...)时， * 就会调用key_read函数 */ static int key_read(struct file *filp, char __user *buff, size_t count, loff_t *offp) { unsigned long err; if (!ev_press) { if (filp->f_flags & O_NONBLOCK) return -EAGAIN; else /* 如果ev_press等于0，休眠 */ wait_event_interruptible(key_waitq, ev_press); } /* 执行到这里时，ev_press等于1，将它清0 */ ev_press = 0; /* 将按键状态复制给用户，并清0 */ err = copy_to_user(buff, (const void *)key_values, min(sizeof(key_values), count)); memset((void *)key_values, 0, sizeof(key_values)); return err ? -EFAULT : min(sizeof(key_values), count); } /************************************************** * 当用户程序调用select函数时，本函数被调用 * 如果有按键数据，则select函数会立刻返回 * 如果没有按键数据，本函数使用poll_wait等待 **************************************************/ static unsigned int key_poll(struct file *file, struct poll_table_struct *wait) { unsigned int mask = 0; poll_wait(file, &key_waitq, wait); if (ev_press) mask |= POLLIN | POLLRDNORM; return mask; } /* 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的对应函数 */ static struct file_operations key_fops = { .owner = THIS_MODULE, /* 这是一个宏，指向编译模块时自动创建的__this_module变量 */ .open = key_open, .release = key_close, .read = key_read, .poll = key_poll, }; void set_gpio_mode_for_key(struct key_desc_t * key) { int i; for(i = 0; i < MAX_KEYS; i ++,key ++) { //s3c_gpio_pullup(key->pin, 1); s3c_gpio_cfgpin(key->pin, key->pin_dir); } } /* * Set up the cdev structure for a device. */ static void key_setup_cdev(struct key_dev *dev, int minor) { printk("in the key_setup_cdev!!\n"); int err, devno = MKDEV(key_major, minor); cdev_init(&dev->cdev, &key_fops); //dev->cdev.owner = THIS_MODULE; //dev->cdev.ops = &key_fops; printk("cdev_init success!!\n"); err = cdev_add (&dev->cdev, devno, 1); /* Fail gracefully if need be */ if (err) printk (KERN_NOTICE "Error %d adding key%d", err, minor); printk("key_setup_cdev success!!\n"); } /* * We export one key device. There's no need for us to maintain any * special housekeeping info, so we just deal with raw cdev. */ //static struct cdev key_cdev; /* * 执行“insmod *.ko”命令时就会调用这个函数 */ static int __init button_init(void) { int result; dev_t dev = MKDEV(key_major, 0); char dev_name[]="key"; /*申请gpio*/ int ret; int i=0; for(i=0;i<MAX_KEYS;i++) { ret=gpio_request(key_desc[i].pin,"KEY"); if(ret) { printk("fail to request gpio %d !!\n",key_desc[i].pin); return 0; } } printk("request gpio success!!\n"); /* Figure out our device number. */ if (key_major) result = register_chrdev_region(dev, 1, dev_name); else { result = alloc_chrdev_region(&dev, 0, 1, dev_name); key_major = MAJOR(dev); } if (result < 0) { printk(KERN_WARNING "key: unable to get major %d\n", key_major); return result; } if (key_major == 0) key_major = result; printk("alloc_chrdev_region success !!\n"); /* 动态申请设备结构体的内存*/ key_devp = kmalloc(sizeof(struct key_dev), GFP_KERNEL);//kmalloc()内核空间；malloc()用户空间。返回起始地址 if (!key_devp) /*申请失败*/ { result = - ENOMEM; printk("key_devp kmalloc failed!!\n"); } memset(key_devp, 0, sizeof(struct key_dev));//把此内存空间清零 /* Now set up cdev. */ key_setup_cdev(key_devp, 0); printk("key device installed, with major %d\n", key_major); printk("The device name is: /dev/%s\n", dev_name); /*set gpio mode*/ //set_gpio_mode_for_key(key_desc); /*init kernel timer*/ init_timer(&key_devp->key_timer); key_devp->key_timer.function = &key_timer_handle; key_devp->key_timer.data = (unsigned long)key_desc; key_devp->key_timer.expires = jiffies + KEY_TIMER_DELAY; add_timer(&key_devp->key_timer); /*用udev机制自动添加设备结点*/ key_class=class_create(THIS_MODULE,"key_class"); device_create(key_class,NULL,key_devp->cdev.dev,NULL,dev_name); return 0; } /* * 执行rmmod key_drv.ko”命令时就会调用这个函数 */ static void __exit button_cleanup(void) { cdev_del(&key_devp->cdev); unregister_chrdev_region(MKDEV(key_major, 0), 1); del_timer_sync(&key_devp->key_timer); printk("key device uninstalled\n"); } /* 这两行指定驱动程序的初始化函数和卸载函数 */ module_init(button_init); module_exit(button_cleanup); /* 描述驱动程序的一些信息，不是必须的 */ MODULE_AUTHOR("mhb@SEU"); // 驱动程序的作者 MODULE_DESCRIPTION("KEY Driver"); // 一些描述信息 MODULE_LICENSE("GPL"); // 遵循的协议
测试代码：
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/ioctl.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <sys/select.h> #include <sys/time.h> #include <errno.h> int main(void) { int i; int key_fd; int key_value[5]; /*打开键盘设备文件*/ key_fd = open("/dev/key", 0); if (key_fd < 0) { perror("open device key"); exit(1); } for (;;) { fd_set rds; int ret; FD_ZERO(&rds); FD_SET(key_fd, &rds); /*使用系统调用select检查是否能够从/dev/key设备读取数据*/ ret = select(key_fd + 1, &rds, NULL, NULL, NULL); /*读取出错则退出程序*/ if (ret < 0) { perror("select"); exit(1); } if (ret == 0) { printf("Timeout.\n"); } /*能够读取到数据*/ else if (FD_ISSET(key_fd, &rds)) { /*开始读取键盘驱动发出的数据，注意key_value和键盘驱动中定义为一致的类型*/ int ret = read(key_fd, key_value, sizeof key_value); if (ret != sizeof key_value) { if (errno != EAGAIN) perror("read key\n"); continue; } else { /*打印键值*/ for (i = 0; i < 5; i++) printf("K%d %s, key value = 0x%02x\n", \ i+1, (key_value[i] & 0x80) ? "released": \ key_value[i] ? "pressed down" : "", key_value[i]); } } } /*关闭设备文件句柄*/ close(key_fd); return 0; }
