按键驱动——查询方式实现
OK6410总共有6个按键，按键分别接在GPN0~GPN5,原理图上根本没有这么说，原理图上说的是KEYINT!~KEYINT6,很明显这里是接在中断引脚上的，直接查询S3C6410的中断引脚就可以知道这个6个按键的接法，一下是用查询方法实现的按键驱动：
#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 <mach/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/device.h>//新版内核
static struct class *key_drv_class;
static struct class_device *key_class_dev;
volatile unsigned long *gpncon=NULL;
volatile unsigned long *gpndat=NULL;
static int key_drv_open(struct inode * inode, struct file * file)
{
*gpncon &=~((0x3<<0)|(0x3<<2)|(0x3<<4)|(0x3<<6));
return 0;
}
static ssize_t key_drv_write(struct inode * file, const char __user *buf, size_t count, loff_t *ppos)
{
return 0;
}
ssize_t key_drv_read (struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
//返回四个引脚的电平
unsigned char key_val[4];
int regval;
if(size != sizeof(key_val))
return -EINVAL;
regval=*gpndat;
key_val[0] = (regval & (1<<0))?1:0;
key_val[1] = (regval & (1<<1))?1:0;
key_val[2] = (regval & (1<<2))?1:0;
key_val[3] = (regval & (1<<3))?1:0;
copy_to_user(buf,key_val,sizeof(key_val));
return sizeof(key_val);
}
static struct file_operations key_drv_openration ={
.owner = THIS_MODULE,
.open = key_drv_open,
.write =key_drv_write,
.read=key_drv_read,
};
int major;
static int key_drv_init(void)
{
major=register_chrdev(0,"key_drv",&key_drv_openration);
key_drv_class = class_create(THIS_MODULE, "key_drv");
//自动创建设备节点
/* 新版的内核不能用class_device_create 要用device_create*/
key_class_dev = device_create(key_drv_class, NULL, MKDEV(major, 0), NULL, "key"); /* /dev/xyz */
gpncon = (volatile unsigned long*)ioremap(0x7F008830,16);
gpndat=gpncon+1;//指针的操作是按照指针指向的长度为单位?
/*本例中使用的是unsigned long类型刚好是4个字节*/
return 0;
}
static void key_drv_exit(void)
{
unregister_chrdev(major,"key_drv");
device_unregister(key_class_dev);
class_destroy(key_drv_class);
iounmap(gpncon);
return 0;
}
module_init(key_drv_init);
module_exit(key_drv_exit);
MODULE_LICENSE("GPL");
一下是测试程序：
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdio.h>
int main(int argc,char **argv)
{
int fd;
unsigned char key_val[4];
int cnt;
fd=open("/dev/key",O_RDWR);
if(fd < 0)
printf("can not open!!!\n");
while(1)
{
read(fd,key_val,sizeof(key_val));
if(!key_val[0]||!key_val[1]||!key_val[2]||!key_val[3])
{
printf("%04d key pressed :%d %d %d %d\n\n",cnt++,key_val[0],key_val[1],key_val[2],key_val[3]);
}
}
return 0;
}
一下是测试运行结果：
1452 key pressed :1 0 1 1
1453 key pressed :1 0 1 1
1454 key pressed :1 0 1 1
1455 key pressed :1 0 1 1
1456 key pressed :1 0 1 1
1457 key pressed :1 0 1 1
1458 key pressed :1 0 1 1
1459 key pressed :1 0 1 1
1460 key pressed :1 0 1 1
1461 key pressed :1 0 1 1
让测试程序后台运行，查看CPU的运行状态：
Mem: 7968K used, 246548K free, 0K shrd, 0K buff, 2096K cached
CPU: 9.1% usr 90.8% sys 0.0% nic 0.0% idle 0.0% io 0.0% irq 0.0% sirq
Load average: 0.34 0.13 0.07 2/25 984
PID PPID USER STAT VSZ %VSZ CPU %CPU COMMAND
983 969 root R 792 0.3 0 99.6 ./main
984 969 root R 2268 0.8 0 0.2 top
969 1 root S 2268 0.8 0 0.0 -/bin/sh
1 0 root S 2264 0.8 0 0.0 init
4 2 root SW 0 0.0 0 0.0 [kworker/0:0]
5 2 root SW 0 0.0 0 0.0 [kworker/u:0]
可以看出按键 程序的CPU占用率很大，这种驱动方式很不好。