一步一步学驱动(2)

目标：编写一个按键驱动程序，如果有按键按下就打印一些信息。

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 <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>

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;

static struct class *btn_cls; //为了自动创建设备节点
static struct class_device *btn_cls_dev; //为了自动创建设备节点
static struct cdev cdev;
static int major = 0;

static int btn_open(struct inode *inode, struct file *file)
{
    *gpfcon &= ~((0x3 <<(2*0)) | (0x3 << (2*1)) | (0x3 <<(2*2))//设置按键的引脚为输入引
                | (0x3 << (2*4)));                             //角

    return 0;
}
ssize_t btn_read(struct file *file, char __user * buf,
         size_t len, loff_t * ppos)
{
    unsigned long rev;
    unsigned char key_val[4];

    if (len != sizeof(key_val))
        return -EINVAL;

    rev = *gpfdat; //读取寄存器的值
    key_val[0] = (rev & (1<<0)) ? 0 : 1;//获取K4的状态，是否按下
    key_val[1] = (rev & (1<<1)) ? 0 : 1;//获取K1的状态，是否按下
    key_val[2] = (rev & (1<<2)) ? 0 : 1;//获取K3的状态，是否按下
    key_val[3] = (rev & (1<<4)) ? 0 : 1;//获取K2的状态，是否按下

    copy_to_user(buf, key_val, sizeof(key_val));

    return 0;
}
static int btn_release(struct inode *inode, struct file *file)
{
    printk("button release\n");
    return 0;
}


const struct file_operations btn_op =
{
    .owner     = THIS_MODULE,
    .open = btn_open,
    .read = btn_read,
    .release = btn_release,
};

static int btn_val_init()
{
    dev_t devid;
    int rc;
    if (major)
    {
        devid = MKDEV(major, 0);
        rc = register_chrdev_region(devid, 1, "button");
    }
    else
    {
        rc = alloc_chrdev_region(&devid, 0, 1, "button");
        major = MAJOR(devid);
    }

    if (rc < 0)
    {
        printk(KERN_ERR, "can't get major");
        return -ENODEV;
    }

    cdev_init(&cdev, &btn_op);
    cdev_add(&cdev, devid, 1);

    btn_cls = class_create(THIS_MODULE, "button");
    btn_cls_dev = class_device_create(btn_cls, NULL, MKDEV(major, 0), NULL, "button0");//这个button0才是自动创建的设备节点的名字，可以和其他的名字不一样，见上面

    gpfcon = (volatile unsigned long)ioremap(0x56000050, 16);//GPFCON寄存器的地址映射
    gpfdat = gpfcon 1;

    return 0;
}

static void btn_val_exit()
{
    class_device_destroy(btn_cls, MKDEV(major, 0));
    class_destroy(btn_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("read the value of button");
MODULE_LICENSE("GPL");

运行结果：

 

 

测试小例子：

 

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

int main()
{
    int fd;
    unsigned char key_val[4];

    fd = open("/dev/button0", O_RDWR);//这个名字是 class_device_create 时的名字
    if (fd < 0)
    {
        printf("open /dev/button0 failed\n");
        return -1;
    }
    while (1)
    {
        read(fd, key_val, sizeof(key_val));
        if (key_val[0] || key_val[1] || key_val[2] || key_val[3])
        {
            printf("key[0] = %d, key[1] = %d, key[2] = %d, key[3] = %d\n",
                key_val[0], key_val[1], key_val[2], key_val[3]);
        }
    }

    return 0;
}

运行结果：

当按下按键时就会打印一些信息

 

 

                图1 TQ2440底板原理图

 

 

   图2 TQ2440核心板原理图

 

  图3.s3c2440.pdf

 

图4.s3c2440.pdf