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

原理圖:

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驅動程序代碼：

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為輸入引腳 */*gpfcon &= ~((0x3<<(0*2)) | (0x3<<(2*2)));/* 配置GPG3,11為輸入引腳 */*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個引腳的電平 */unsigned char key_vals[4];int regval;if (size != 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, /* 這是一個宏，推向編譯模塊時自動創建的__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", &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");

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應用程序代碼：

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; }

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