一步一步学驱动(4)

目标：上一个例子运行后，如果没有按键按下，应用程序会在read处一直等待，所以这次在上个例子的基础上添加返回功能，即若没有按键按下，在一定时间后会返回。

环境：TQ2440+Ubuntu12.04，linux-2.6.25

 

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/cdev.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/poll.h>

#include <asm/irq.h>
#include <asm/arch/regs-gpio.h>
#include <asm/arch/map.h>
#include <asm/arch/regs-irq.h>
#include <asm/io.h>
#include <asm/hardware.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/hardware.h>



static DECLARE_WAIT_QUEUE_HEAD(button_waitq);


static volatile int ev_press = 0;

static int major = 0;
static struct cdev cdev;
static struct class *cls;
static struct class_device *cls_dev;

struct pin_dec
{
    unsigned int irq;
    unsigned int pin;
    unsigned int pin_setting;
    unsigned int key_val;
    char *name;
};

static unsigned int btn;

struct pin_dec pins_dec[4] =
{
    {IRQ_EINT0, S3C2410_GPF0, S3C2410_GPF0_EINT0, 0, "S4"},
    {IRQ_EINT1, S3C2410_GPF1, S3C2410_GPF1_EINT1, 1, "S1"},
    {IRQ_EINT2, S3C2410_GPF2, S3C2410_GPF2_EINT2, 2, "S3"},
    {IRQ_EINT4, S3C2410_GPF4, S3C2410_GPF4_EINT4, 3, "S2"},
};


static irqreturn_t btn_val_irq(int irq, void *dev_id)
{
    struct pin_dec *pin = (struct pin_dec *)dev_id;
    int res;
    res = s3c2410_gpio_getpin(pin->pin);
    if (!res)
    {
        btn = pin->key_val | 0x80;
    }
    else
    {
        btn = pin->key_val;
    }

    ev_press = 1;
    wake_up_interruptible(&button_waitq); /* 唤醒休眠的进程 */


    return IRQ_RETVAL(IRQ_HANDLED);
}


static int btn_val_open(struct inode *inode, struct file *file)
{
    int i;
    for (i = 0; i < 4; i++)
    {
        s3c2410_gpio_cfgpin(pins_dec[i].pin, pins_dec[i].pin_setting);
        request_irq(pins_dec[i].irq, btn_val_irq, IRQT_BOTHEDGE, pins_dec[i].name, &pins_dec[i]);
    }

    return 0;
}

ssize_t btn_val_read(struct file *file, char __user * buf,
         size_t len, loff_t * ppos)
{
    wait_event_interruptible(button_waitq, ev_press);

    /* 如果有按键动作, 返回键值 */
    copy_to_user(buf, &btn, 1);
    ev_press = 0;

    return 1;
    return 0;
}

static int btn_val_release(struct inode *inode, struct file *file)
{
    int i;
    for (i = 0; i < 4; i++)
    {
        free_irq(pins_dec[i].irq, &pins_dec[i]);
    }
    return 0;
}

static unsigned int btn_val_poll(struct file *fp, poll_table * wait)
{
    unsigned int mask = 0;

    poll_wait(fp, &button_waitq, wait);
    if (ev_press)
        mask |= POLLIN | POLLRDNORM;
    return mask;
}



const struct file_operations fops =
{
    .owner = THIS_MODULE,
    .open = btn_val_open,
    .read = btn_val_read,
    .poll = btn_val_poll,
    .release = btn_val_release,
};

static int btn_val_init()
{
    dev_t devid;
    int rec;

    if (major)
    {
        devid = MKDEV(major, 0);
        rec = register_chrdev_region(devid, 1, "button2");
    }
    else
    {
        rec = alloc_chrdev_region(&devid, 0, 1, "button2");
        major = MAJOR(devid);
    }
    if (rec < 0)
    {
        printk(KERN_ERR, "can't get major");
        return -ENODEV;
    }
    cdev_init(&cdev, &fops);
    cdev_add(&cdev, devid, 1);

    cls = class_create(THIS_MODULE, "button2");
    cls_dev = class_device_create(cls, NULL, MKDEV(major, 0), NULL, "button2");


    return 0;
}

static void btn_val_exit()
{
    class_device_destroy(cls, MKDEV(major, 0));
    class_destroy(cls);
    cdev_del(&cdev);
    unregister_chrdev_region(MKDEV(major, 0), 1);
}

module_init(btn_val_init);
module_exit(btn_val_exit);

MODULE_AUTHOR("xiaoming");
MODULE_DESCRIPTION("interrupt button value");
MODULE_LICENSE("GPL");

运行结果：

测试小例子：

 

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


int main(int argc, char **argv)
{
    int fd;
    unsigned char key_val;
    int ret;

    struct pollfd fds[1];

    fd = open("/dev/button2", O_RDWR);
    if (fd < 0)
    {
        printf("can't open /dev/button2 !\n");
    }

    fds[0].fd = fd;
    fds[0].events = POLLIN;
    while (1)
    {
        ret = poll(fds, 1, 5000);
        if (ret == 0)
        {
            printf("time out!\n");
        }
        else
        {
            read(fd, &key_val, 1);
            printf("key_val=0x%x\n", key_val);
        }
    }

    return 0;
}

运行结果：

当没有按键按下时，每隔5秒就会打印一次time out!当有按键按下时会立刻打印键值