Linux字符设备驱动之按键驱动（TQ210）

TQ210共有8个通用按键，分别连接XEINT0~5（即GH0_0~GPH0_5）和XENIT22~23（即GPH2_6、GPH2_7），

韦东山第2个驱动是死循环查询按键
第3个是中断法+等待队列（阻塞），当应用程序读按键值时，如果没有按键按下，则app进入休眠，当有按键按下，驱动中的中断服务程序，唤醒app，从而获取按键值。
第4个是poll机制。中断法有个缺点：app的读操作一直是存在的，加入poll机制可以让app在有按键按下的时候才执行读按键操作。
当应用程序读按键值时，如果没有按键按下，则app并不会立即进入休眠，而是当5秒之内都没有按键按下时，app才进入休眠。
第5个增加异步通知
第6个增加信号量操作（互斥锁、原子操作）
第7个增加输入子系统

代码很简单,先看看加了poll机制的代码.
button_drv.c:

/*
 * linux/drivers/char/gec210_buttons.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/interrupt.h>
#include <asm/uaccess.h>
#include <mach/hardware.h>
#include <linux/platform_device.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>

#include <mach/map.h>
#include <mach/gpio.h>
#include <mach/regs-clock.h>
#include <mach/regs-gpio.h>

#include <linux/gpio.h>//gpio结构体的定义
#include <linux/sched.h>//
// #include <linux/wait.h>

#define DEVICE_NAME        "buttons"

struct button_desc {
    int gpio;
    int number;
    char *name;
    struct timer_list timer;
};

static struct button_desc buttons[] = {
    { S5PV210_GPH0(0), 0, "KEY0" },
    { S5PV210_GPH0(1), 1, "KEY1" },
    { S5PV210_GPH0(2), 2, "KEY2" },
    { S5PV210_GPH0(3), 3, "KEY3" },
    { S5PV210_GPH0(4), 4, "KEY4" },
    { S5PV210_GPH0(5), 5, "KEY5" },
    { S5PV210_GPH2(6), 6, "KEY6" },
    { S5PV210_GPH2(7), 7, "KEY7" },
};

static volatile char key_values[] = {
    '0', '0', '0', '0', '0', '0', '0', '0'
};

static DECLARE_WAIT_QUEUE_HEAD(button_waitq);

static volatile int ev_press = 0;

//使用定时器消抖
static void gec210_buttons_timer(unsigned long _data)
{
    struct button_desc *bdata = (struct button_desc *)_data;
    int down;
    int number;
    unsigned tmp;

    tmp = gpio_get_value(bdata->gpio);

    /* active low */
    down = !tmp;
    printk("KEY %d: %08x\n", bdata->number, down);

    number = bdata->number;
    if (down != (key_values[number] & 1)) {
        key_values[number] = '0' + down;

        ev_press = 1;
        wake_up_interruptible(&button_waitq);
    }
}

//定时器中断
static irqreturn_t button_interrupt(int irq, void *dev_id)
{
    struct button_desc *bdata = (struct button_desc *)dev_id;

    mod_timer(&bdata->timer, jiffies + msecs_to_jiffies(40));

    return IRQ_HANDLED; // return 1
}

static int gec210_buttons_open(struct inode *inode, struct file *file)
{
    int irq;
    int i;
    int err = 0;
    //注册8个中断
    for (i = 0; i < ARRAY_SIZE(buttons); i++) {
        if (!buttons[i].gpio)
            continue;

        setup_timer(&buttons[i].timer, gec210_buttons_timer,
                (unsigned long)&buttons[i]);
        //从io获取中断信号线
        irq = gpio_to_irq(buttons[i].gpio);
        //申请按键中断, 边沿触发中断
        err = request_irq(irq, button_interrupt, IRQ_TYPE_EDGE_BOTH,
                buttons[i].name, (void *)&buttons[i]);
        if (err)
            break;
    }

    if (err) {
        i--;
        for (; i >= 0; i--) {
            if (!buttons[i].gpio)
                continue;

            irq = gpio_to_irq(buttons[i].gpio);
            disable_irq(irq);
            free_irq(irq, (void *)&buttons[i]);

            del_timer_sync(&buttons[i].timer);
        }

        return -EBUSY;
    }

    ev_press = 1;
    return 0;
}

static int gec210_buttons_close(struct inode *inode, struct file *file)
{
    int irq, i;

    for (i = 0; i < ARRAY_SIZE(buttons); i++) {
        if (!buttons[i].gpio)
            continue;

        irq = gpio_to_irq(buttons[i].gpio);
        free_irq(irq, (void *)&buttons[i]);

        del_timer_sync(&buttons[i].timer);
    }

    return 0;
}

static int gec210_buttons_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
            wait_event_interruptible(button_waitq, ev_press);
    }

    ev_press = 0;

    err = copy_to_user((void *)buff, (const void *)(&key_values),
            min(sizeof(key_values), count));

    return err ? -EFAULT : min(sizeof(key_values), count);
}

static unsigned int gec210_buttons_poll( struct file *file,
        struct poll_table_struct *wait)
{
    unsigned int mask = 0;

    poll_wait(file, &button_waitq, wait);
    if (ev_press)
        mask |= POLLIN | POLLRDNORM;

    return mask;
}

static struct file_operations dev_fops = {
    .owner        = THIS_MODULE,
    .open        = gec210_buttons_open,
    .release    = gec210_buttons_close,
    .read        = gec210_buttons_read,
    .poll        = gec210_buttons_poll,
};

static struct miscdevice misc = {
    .minor        = MISC_DYNAMIC_MINOR,
    .name        = DEVICE_NAME,
    .fops        = &dev_fops,
};

static int __init button_dev_init(void)
{
    int ret;

    ret = misc_register(&misc);

    printk(DEVICE_NAME"\tinitialized\n");

    return ret;
}

static void __exit button_dev_exit(void)
{
    misc_deregister(&misc);
}

module_init(button_dev_init);
module_exit(button_dev_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("GEC Inc.");

buttontest.c：

#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>

#define  ARRY_SIZE(x) (sizeof(x)/sizeof(x[0]))

int main(int argc , char **argv)
{
    int button_fd ;
    char current_button_value[8]={0}; //板载八个按键 key2-9
    char prior_button_value[8]={0};        //用于保存按键的前键值

    button_fd = open("/dev/buttons",O_RDONLY);
    if(button_fd <0){
        perror("open device :");
        exit(1);
    }

    while(1){
        int i ;

        if (read(button_fd, current_button_value, sizeof(current_button_value)) != sizeof(current_button_value)) {
            perror("read buttons:");
            exit(1);
        }

        for(i = 0;i < ARRY_SIZE(current_button_value);i++){
            if(prior_button_value[i] != current_button_value[i]){        //判断当前获得的键值与上一的键值是否一致，以判断按键有没有被按下或者释放
                prior_button_value[i] = current_button_value[i];

                switch(i){
                    case 0:
                        printf("BACK \t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 1:
                        printf("HOME \t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 2:
                        printf("MENU \t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 3:
                        printf("UP \t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 4:
                        printf("DOWN \t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 5:
                        printf("ENTER\t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 6:
                        printf("LEFT\t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    case 7:
                        printf("RIGHT \t%s\n",current_button_value[i]=='0'?"Release":"Pressed");
                        break;
                    default:
                        printf("\n");
                        break;
                }
            }
        }

    }

    return 0;
}

Makefile:

KERN_DIR = /home/richard/work/kernel/linux-3.10.80
obj-m += button_drv.o

all:
    make -C $(KERN_DIR) M=`pwd` modules
    arm-linux-gnueabi-gcc -o buttontest buttontest.c
clean:
    rm -rf *.ko *.mod.c *.mod.o *.o *.order *.symvers *.cmd .*.o.* .*.ko.*