12.重写按键驱动-轮询查询

按键驱动编写步骤：

1.驱动框架

2.硬件资料查询

3.代码：

        一：轮询查找

        二：中断方式

        三：poll机制

        四：异步通知

        五：同步互斥阻塞

轮询查找方式：

一.驱动框架

#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_buttons_class;
static struct class_device *seconddrv_buttons_class_dev;

static int seconddrv_buttons_open(struct inode *inode, struct file *file)
{
    printk("seconddrv_open\n");
    return 0;
}
static int seconddrv_buttons_read(struct file *filp, char __user *buff,size_t count, loff_t *offp)
{
    printk("seconddrv_read\n");
    return 0;
}
static struct file_operations seconddrv_buttons_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   =   seconddrv_buttons_open,           
    .read    =    seconddrv_buttons_read,      
};
int major;
int seconddrv_buttons_init(void)
{
    major = register_chrdev(0,"seconddrv",&seconddrv_buttons_fops);
    seconddrv_buttons_class = class_create(THIS_MODULE,"buttons");
    seconddrv_buttons_class_dev = class_device_create(seconddrv_buttons_class,NULL,MKDEV(major,0),NULL,"mybuttons");

    return 0;
}

void seconddrv_buttons_exit(void)
{
    unregister_chrdev(major,"seconddrv");
    class_destroy(seconddrv_buttons_class);
    class_device_unregister(seconddrv_buttons_class_dev);
    return 0;
}
module_init(seconddrv_buttons_init);
module_exit(seconddrv_buttons_exit);
MODULE_LICENSE("GPL");

二.硬件资料查询

1.原理图查看引脚

2.查询物理地址和寄存器资料

我们先用轮询查询的方式，不用中断方式，所以引脚要设置为输入模式，参考芯片手册

物理地址：

GPFCON寄存器和GPGCON寄存器：

GPFDAT寄存器和GPGDAT寄存器：

三.硬件代码编写

思路：先把控制寄存器设置为输入模式，定义四个按键值，读取四个按键值，返回用户空间，在用户空间循环读取和打印信息

static int seconddrv_buttons_open(struct inode *inode, struct file *file)
{
    /*配置GPF0,2为输入引脚*/
    *gpfcon &=~((0x03<<(0*2))|(0x03<<(2*2)));
    /*配置GPG3,11为输入引脚*/
    *gpgcon &=~((0x03<<(2*3))|(0x03<<(2*11)));
    
    //printk("seconddrv_open\n");
    return 0;
}
ssize_t seconddrv_buttons_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 seconddrv_buttons_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   =   seconddrv_buttons_open,           
    .read    =    seconddrv_buttons_read,     
};
int major;
int seconddrv_buttons_init(void)
{
    major = register_chrdev(0,"seconddrv",&seconddrv_buttons_fops);
    seconddrv_buttons_class = class_create(THIS_MODULE,"buttons");
    seconddrv_buttons_class_dev = class_device_create(seconddrv_buttons_class,NULL,MKDEV(major,0),NULL,"mybuttons");
    
    gpfcon = (volatile unsigned long *)ioremap(0x56000050,16);
    gpfdat = gpfcon + 1;

    gpgcon = (volatile unsigned long *)ioremap(0x56000060,16);
    gpgdat = gpgcon +1;
    
    return 0;
}

四.测试代码：

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
/*
*mybuttons_test
*/
int main(int argc, char **argv)
{
    int fd;
    unsigned char key_vals[4];
    int cnt = 0;
    
    fd = open("/dev/mybuttons", 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;
}

结果：