字符设备驱动-轮询方式操控按键

一般驱动都分为两个部分： 一：写出框架 二：硬件操作 框架搭建： ①头文件的拷贝

#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include 

②将open、read驱动函数框架写出

static int second_drv_open(struct inode *inode,struct file *file)
{
    return 0;
}

③定义fileoperation

static struct file_operations second_drv_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  = second_drv_open,
    .read = second_drv_read,
};

④ 入口函数编写(注册驱动程序)

int major; 

static int second_drv_init(void)
{
        major = register_chrdev(0,"second_drv",&second_drv_fops);

        return 0;
}

出口函数编写(卸载驱动程序)

static int second_drv_exit(void)
{
        unregister_chrdev(major,"second_drv");
        return 0;
}

入口函数和出口函数也只是普通的函数，何以达到入口出口的功能！需要通过module_来修饰。

module_init(second_drv_init);
module_exit(second_drv_exit);

⑤给sysfs提供更多信息，利用udev机制创建设备节点 Ⅰ定义两个结构体

static struct class *seconddrv_class;
static struct class_device *seconddrv_class_dev;

Ⅱ 入口函数中创建一个类=>类下面创建一个设备

int major;
static int second_drv_init(void)
{
        major = register_chrdev(0,"second_drv",&second_drv_fops);
        seconddrv_class = class_create(THIS_MODULE,"seconddrv");
        seconddrv_class_dev = class_device_create(seconddrv_class,NULL,MKDEV(major,0),NULL,"buttons");
}

补： mdev是udev的简化版本，mdev应用程序会被内核来调用，根据⑤提供的信息来创建/dev/buttons 设备节点。

Ⅲ 出口函数中卸载类

static int second_drv_exit(void)
{
        unregister_chrdev(major,"second_drv");
        class_device_unregister(seconddrv_class_dev);
        class_destroy(seconddrv_class);
        return 0;
}

⑥ MODULE_LICENSE("GPL");

通过 “GPL” 指明 这是GNU General Public License的任意版本

测试：

修改Makefile
cp second_drv.ko /work/nfs_root/czg
insmod ./second_drv.ko
lsmod
cat /proc/devices
ls /dev/buttons -l

硬件操作 ① 看原理图-确定哪些引脚 ② 看2440手册-确定引脚状态 ③ 编程 Ⅰ单片机：物理地址 Ⅱ 驱动：虚拟地址

VA = ioremap(PA,size)

原理图：

2440手册：

编程： ① 定义寄存器

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;
volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;

② 地址映射建立和解除 入口函数中建立:

static int second_drv_init(void)
{
        major = register_chrdev(0,"second_drv",&second_drv_fops);
        seconddrv_class = class_create(THIS_MODULE,"seconddrv");
        seconddrv_class_dev = class_device_create(seconddrv_class,NULL,MKDEV(major,0),NULL,"buttons");
        gpfcon = (volatile unsigned long *)ioremap(0x56000050,16);
        gpfdat = gpfcon + 1;
        gpgcon = (volatile unsigned long *)ioremap(0x56000060,16);
        gpgdat = gpgcon + 1;
        return 0;
}

出口函数中解除：

static int second_drv_exit(void)
{
        unregister_chrdev(major,"second_drv");
        class_device_unregister(seconddrv_class_dev);
        class_destroy(seconddrv_class);
        iounmap(gpfcon);
        iounmap(gpgcon);
        return 0;
}

③ open函数中配置引脚

static int second_drv_open(struct inode *inode,struct file *file)
{
    /* 配置GPF0,2为输入引脚 */
    *gpfcon &= ~((0x3<<(0*2)) | (0x3<<(2*2)));

    /* 配置GPG3为输入引脚 */
    *gpgcon &= ~((0x3<<(3*2)));

    return 0;
}

④ read函数中返回引脚状态

static ssize_t second_drv_read (struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    /* 返回4个引脚的电平状态 */
    unsigned char key_vals[3];
    int regval;
    //看用户需要读取的空间，和这里的是否相同
    if(count != sizeof(key_vals))
        return -EINVAL;
    /* 读GPF0,2 */
    regval = *gpfdat;
    key_vals[0] = (regval & (1<<0)) ? 1 : 0;
    key_vals[1] = (regval & (1<<2)) ? 1 : 0;
    /* 读GPF3 */
    regval = *gpgdat;
    key_vals[2] = (regval & (1<<3)) ? 1 : 0;

    //将值返回给用户程序
    copy_to_user(buf,key_vals,sizeof(key_vals));
    return sizeof(key_vals);
}

完整代码：

Makefile

KERN_DIR = /work/system/linux-2.6.22.6

all:
    make -C $(KERN_DIR) M=`pwd` modules 

clean:
    make -C $(KERN_DIR) M=`pwd` modules clean
    rm -rf modules.order

obj-m += second_drv.o

驱动程序：second_drv.c

#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include   
#include 

static struct class *seconddrv_class;
static struct class_device *seconddrv_class_dev;

volatile unsigned long *gpfcon;
volatile unsigned long *gpfdat;
volatile unsigned long *gpgcon;
volatile unsigned long *gpgdat;

static int second_drv_open(struct inode *inode,struct file *file)
{
    /* 配置GPF0,2为输入引脚 */
    *gpfcon &= ~((0x3<<(0*2)) | (0x3<<(2*2)));

    /* 配置GPG3为输入引脚 */
    *gpgcon &= ~((0x3<<(3*2)));

    return 0;
}

static ssize_t second_drv_read (struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    /* 返回4个引脚的电平状态 */
    unsigned char key_vals[3];
    int regval;
    //看用户需要读取的空间，和这里的是否相同
    if(count != sizeof(key_vals))
        return -EINVAL;
    /* 读GPF0,2 */
    regval = *gpfdat;
    key_vals[0] = (regval & (1<<0)) ? 1 : 0;
    key_vals[1] = (regval & (1<<2)) ? 1 : 0;
    /* 读GPF3 */
    regval = *gpgdat;
    key_vals[2] = (regval & (1<<3)) ? 1 : 0;

    //将值返回给用户程序
    copy_to_user(buf,key_vals,sizeof(key_vals));
    return sizeof(key_vals);
}

static struct file_operations second_drv_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  = second_drv_open,
    .read = second_drv_read,
};

int major; 

static int second_drv_init(void)
{
        major = register_chrdev(0,"second_drv",&second_drv_fops);
        seconddrv_class = class_create(THIS_MODULE,"seconddrv");
        seconddrv_class_dev = class_device_create(seconddrv_class,NULL,MKDEV(major,0),NULL,"buttons");
        gpfcon = (volatile unsigned long *)ioremap(0x56000050,16);
        gpfdat = gpfcon + 1;
        gpgcon = (volatile unsigned long *)ioremap(0x56000060,16);
        gpgdat = gpgcon + 1;
        return 0;
}

static int second_drv_exit(void)
{
        unregister_chrdev(major,"second_drv");
        class_device_unregister(seconddrv_class_dev);
        class_destroy(seconddrv_class);
        iounmap(gpfcon);
        iounmap(gpgcon);
        return 0;
}

module_init(second_drv_init);
module_exit(second_drv_exit);
MODULE_LICENSE("GPL");

驱动测试程序：seconddrvtest.c

#include   
#include   
#include   
#include   

/* 
 * firstdrvtest
 */

int main(int argc, char **argv)
{
    int fd;
    unsigned char key_vals[3];
    int cnt = 0;
    fd = open("/dev/buttons",O_RDWR);
    if(fd < 0)
    {
        printf("can't open!n");
    }
    while(1)
    {
        read(fd,key_vals,sizeof(key_vals));
        if(!key_vals[0] || !key_vals[1] || !key_vals[2])
        {
            printf("%04d key pressed: %d %d %d.n",cnt++,key_vals[0],key_vals[1],key_vals[2]);
        }

    }

    return 0;
}

测试：

后台运行：./seconddrvtest &
查看后台程序: top
放在前台：fg

insmod second_drv.ko
lsmod
cat /proc/devices
ls /dev/buttons -l
./seconddrvtest