按键查询法驱动程序分析

来源：互联网发布：java 迭代器 for循环编辑：程序博客网时间：2024/06/05 18:59

程序分析

/*目的 按键驱动 查询方式①写出框架           第一步*/           static struct file_operations sencod_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,                        };           //第二步            static int second_drv_open(struct inode *inode, struct file *file){            }            ssize_t second_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos){            }            //第三步 入口函数  修饰入口函数    出口函数  修饰出口函数            static int second_drv_init(void){            register_chrdev(0, "second_drv", &sencod_drv_fops);//注册驱动            }            static void second_drv_exit(void){            unregister_chrdev(major, "second_drv");//卸载驱动               }            module_init(second_drv_init); //修饰让内核识别            module_exit(second_drv_exit);            //第四步 给内核提供更多信息，udev机制可以自动创建设备节点                  // a定义两个结构体                 static struct class *seconddrv_class;                 static struct class_device *seconddrv_class_dev;                 /*b 在入口函数里创建一个类 然后在类里面再创建一个设备*/                  seconddrv_class = class_create(THIS_MODULE, "second_drv");                  seconddrv_class_dev = class_device_create(seconddrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */                      //c 在出口里卸载掉                  class_device_unregister(seconddrv_class_dev);                  class_destroy(seconddrv_class);            //第五步                   MODULE_LICENSE("GPL");//②硬件操作        /* 入口函数进行地址映射         open()配置引脚         read()函数返回引脚状态                   ①定义寄存器*/                   volatile unsigned long *gpfcon;                   volatile unsigned long *gpfdat;                   volatile unsigned long *gpgcon;                   volatile unsigned long *gpgdat;                   //②在入口函数里建立地址映射                   gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);                   gpfdat = gpfcon + 1;                   gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);                   gpgdat = gpgcon + 1;                   //③出口函数解除映射                   iounmap(gpfcon);                   iounmap(gpgcon);                  // ④open函数中配置引脚                   /* 配置GPF0,2为输入引脚 */                  *gpfcon &= ~((0x3<<(0*2)) | (0x3<<(2*2)));                 /* 配置GPG3,11为输入引脚 */                  *gpgcon &= ~((0x3<<(3*2)) | (0x3<<(11*2)));                   //⑤read函数中返回引脚状态                  /* 返回4个引脚的电平 */                  unsigned char key_vals[4];                  int regval;                  if (size != sizeof(key_vals))//判断是否返回成功                  return -EINVAL;              //错误返回              /* 读GPF0,2 */                 regval = *gpfdat;      //如果bit0 =1，则key_vals[0]=1,否则key_vals[0]=0                 key_vals[0] = (regval & (1<<0)) ? 1 : 0;                 key_vals[1] = (regval & (1<<2)) ? 1 : 0;               /* 读GPG3,11 */               regval = *gpgdat;               key_vals[2] = (regval & (1<<3)) ? 1 : 0;               key_vals[3] = (regval & (1<<11)) ? 1 : 0;               copy_to_user(buf, key_vals, sizeof(key_vals));//这些值返回给用户程序               return sizeof(key_vals);  //成功返回

驱动程序

#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/delay.h>#include <asm/uaccess.h>#include <asm/irq.h>#include <asm/io.h>#include <asm/arch/regs-gpio.h>#include <asm/hardware.h>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GPG3,11为输入引脚 */    *gpgcon &= ~((0x3<<(3*2)) | (0x3<<(11*2)));    return 0;}ssize_t second_drv_read(struct file *file, char __user *buf, size_t size, loff_t *ppos){    /* 返回4个引脚的电平 */    unsigned char key_vals[4];    int regval;    if (size != sizeof(key_vals))//判断是否返回成功        return -EINVAL;   //错误返回    /* 读GPF0,2 */    regval = *gpfdat;      //如果bit0 =1，则key_vals[0]=1,否则key_vals[0]=0    key_vals[0] = (regval & (1<<0)) ? 1 : 0;    key_vals[1] = (regval & (1<<2)) ? 1 : 0;    /* 读GPG3,11 */    regval = *gpgdat;    key_vals[2] = (regval & (1<<3)) ? 1 : 0;    key_vals[3] = (regval & (1<<11)) ? 1 : 0;    copy_to_user(buf, key_vals, sizeof(key_vals));//这些值返回给用户程序    return sizeof(key_vals);  //成功返回}static struct file_operations sencod_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", &sencod_drv_fops);    seconddrv_class = class_create(THIS_MODULE, "second_drv");    seconddrv_class_dev = class_device_create(seconddrv_class, NULL, MKDEV(major, 0), NULL, "buttons"); /* /dev/buttons */    gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);    gpfdat = gpfcon + 1;    gpgcon = (volatile unsigned long *)ioremap(0x56000060, 16);    gpgdat = gpgcon + 1;    return 0;}static void 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");

测试程序

#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>/* seconddrvtest   */int main(int argc, char **argv){    int fd;    unsigned char key_vals[4];//定义读出的键值保存的数组    int cnt = 0;    fd = open("/dev/buttons", O_RDWR);    //打开的设备    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] || !key_vals[3])//判断按键是否按下        {            printf("%04d key pressed: %d %d %d %d\n", cnt++, key_vals[0], key_vals[1], key_vals[2], key_vals[3]);        }    }    return 0;}

0 0