arm 驱动基础：查询方式的按键驱动程序

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http://www.cnblogs.com/ITmelody/archive/2012/05/16/2504069.html

原理图:

驱动程序代码：

second_drv.c
#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))        return -EINVAL;    /* 读GPF0,2 */    regval = *gpfdat;    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));        return sizeof(key_vals);}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");

应用程序代码：

seconddrvtest.c
#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];    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] || !key_vals[3])        {            printf("%04d key pressed: %d %d %d %d\n", cnt++, key_vals[0], key_vals[1], key_vals[2], key_vals[3]);        }    }        return 0;}