按键驱动_查询方式

查询方式编写按键驱动. 主要联系copy_to_user接口的使用方法.

copy_to_user(void *to, const void __user *from, unsigned long n);

to : 用户空间指针

from : 内核空间指针

n : 需要拷贝的字节数

成功返回0 , 失败返回未发送成功的字节数.

#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");