字符設備驅(qū)動-輪詢方式操控按鍵

時間：2019-10-09 14:48:20

關鍵字：框架硬件

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[導讀]一般驅(qū)動都分為兩個部分：一：寫出框架二：硬件操作框架搭建： ①頭文件的拷貝 #include #include #include #include #i

一般驅(qū)動都分為兩個部分：一：寫出框架二：硬件操作框架搭建： ①頭文件的拷貝

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

②將open、read驅(qū)動函數(shù)框架寫出

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

③定義fileoperation

static struct file_operations second_drv_fops = {
    .owner = THIS_MODULE,   /* 這是一個宏，推向編譯模塊時自動創(chuàng)建的__this_module變量 */
    .open  = second_drv_open,
    .read = second_drv_read,
};

④ 入口函數(shù)編寫(注冊驅(qū)動程序)

int major; 

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

        return 0;
}

出口函數(shù)編寫(卸載驅(qū)動程序)

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

入口函數(shù)和出口函數(shù)也只是普通的函數(shù)，何以達到入口出口的功能！需要通過module_來修飾。

module_init(second_drv_init);
module_exit(second_drv_exit);

⑤給sysfs提供更多信息，利用udev機制創(chuàng)建設備節(jié)點 Ⅰ定義兩個結構體

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

Ⅱ 入口函數(shù)中創(chuàng)建一個類=>類下面創(chuàng)建一個設備

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");
}

補： mdev是udev的簡化版本，mdev應用程序會被內(nèi)核來調(diào)用，根據(jù)⑤提供的信息來創(chuàng)建/dev/buttons 設備節(jié)點。

Ⅲ 出口函數(shù)中卸載類

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");

通過 “GPL” 指明這是GNU General Public License的任意版本

測試：

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 看原理圖-確定哪些引腳 ② 看2440手冊-確定引腳狀態(tài) ③ 編程 Ⅰ單片機：物理地址 Ⅱ 驅(qū)動：虛擬地址

VA = ioremap(PA,size)

原理圖：

2440手冊：

編程： ① 定義寄存器

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數(shù)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;
}

出口函數(shù)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函數(shù)中配置引腳

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

    /* 配置GPG3為輸入引腳 */
    *gpgcon &= ~((0x3<<(3*2)));

    return 0;
}

④ read函數(shù)中返回引腳狀態(tài)

static ssize_t second_drv_read (struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
    /* 返回4個引腳的電平狀態(tài) */
    unsigned char key_vals[3];
    int regval;
    //看用戶需要讀取的空間，和這里的是否相同
    if(count != sizeof(key_vals))
        return -EINVAL;
    /* 讀GPF0,2 */
    regval = *gpfdat;
    key_vals[0] = (regval & (1<<0)) ? 1 : 0;
    key_vals[1] = (regval & (1<<2)) ? 1 : 0;
    /* 讀GPF3 */
    regval = *gpgdat;
    key_vals[2] = (regval & (1<<3)) ? 1 : 0;

    //將值返回給用戶程序
    copy_to_user(buf,key_vals,sizeof(key_vals));
    return sizeof(key_vals);
}

完整代碼：

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

驅(qū)動程序：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為輸入引腳 */
    *gpfcon &= ~((0x3<<(0*2)) | (0x3<<(2*2)));

    /* 配置GPG3為輸入引腳 */
    *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個引腳的電平狀態(tài) */
    unsigned char key_vals[3];
    int regval;
    //看用戶需要讀取的空間，和這里的是否相同
    if(count != sizeof(key_vals))
        return -EINVAL;
    /* 讀GPF0,2 */
    regval = *gpfdat;
    key_vals[0] = (regval & (1<<0)) ? 1 : 0;
    key_vals[1] = (regval & (1<<2)) ? 1 : 0;
    /* 讀GPF3 */
    regval = *gpgdat;
    key_vals[2] = (regval & (1<<3)) ? 1 : 0;

    //將值返回給用戶程序
    copy_to_user(buf,key_vals,sizeof(key_vals));
    return sizeof(key_vals);
}

static struct file_operations second_drv_fops = {
    .owner = THIS_MODULE,   /* 這是一個宏，推向編譯模塊時自動創(chuàng)建的__this_module變量 */
    .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");

驅(qū)動測試程序：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;
}

測試：