Linux嵌入式驱动学习之路⑩字符设备驱动-my_led

Posted 2020-08-15 叶念西风

首先贴上代码：

字符设备驱动代码：

/**
　*file name: led.c 
　*/
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/wait.h>
#include <linux/mutex.h>
#include <linux/io.h>

#include <linux/fs.h>

static struct class *led_class;     　　　　　　　　//创建类
static struct class_device *led_class_devs[4];    //创建类对应的设备  1个总设备文件  3个单个灯的设备文件

volatile unsigned long *gpfcon = NULL;
volatile unsigned long *gpfdat = NULL;

int led_open(struct inode *inode, struct file *fp)
{
    int minor = MINOR(inode->i_rdev);　　　　　　　　//获取打开设备文件的次设备号
    switch(minor)
    {
        case 0:
            *gpfcon &= ~((0x3<<(4*2))|(0x3<<(5*2))|(0x3<<(6*2)));
            *gpfcon |= (0x1<<(4*2))|(0x1<<(5*2))|(0x1<<(6*2));
            break;
        case 1:
            *gpfcon &= ~(0x3<<(4*2));
            *gpfcon |= (0x1<<(4*2));
            break;
        case 2:
            *gpfcon &= ~(0x3<<(5*2));
            *gpfcon |= (0x1<<(5*2));
            break;
        case 3:
            *gpfcon &= ~(0x3<<(6*2));
            *gpfcon |= (0x1<<(6*2));
            break;
    }
    return 0;
}

ssize_t led_read(struct file *fp, char __user *c, size_t *t){
    int minor = MINOR(fp->f_dentry->d_inode->i_rdev);
    char leds_status;
    switch(minor)
    {
        case 0:
            leds_status = (~((*gpfdat & ((1<<4)|(1<<5)|(1<<6)))>>4))&0x7;
            copy_to_user(buff,(const void *)&leds_status,1);　　　　//将数据从用户拷贝到内核空间
            break;
        case 1:
            leds_status = (~(*gpfdat>>4))&0x1;
            copy_to_user(buff,(const void *)&leds_status,1);
            break;
        case 2:
            leds_status = (~(*gpfdat>>5))&0x1;
            copy_to_user(buff,(const void *)&leds_status,1);
            break;
        case 3:
            leds_status = (~(*gpfdat>>6))&0x1;
            copy_to_user(buff,(const void *)&leds_status,1);
            break;
    }
}

ssize_t led_write(struct file *fp, const char __user *buf, size_t count, loff_t *ppos){
    int minor = MINOR(fp->f_dentry->d_inode->i_rdev);
    int val;
    copy_from_user(&val, buf, 1);
    switch(minor)
    {
        case 0:
            val &= 0x1;
            *gpfdat &= ~((1<<4)|(1<<5)|(1<<6));
            *gpfdat |= (val<<4)|(val<<5)|(val<<6);
            break;
        case 1:
            *gpfdat &= ~(1<<4);
            *gpfdat |= (val&0x1)<<4;
            break;
   
        case 2:
            *gpfdat &= ~(1<<5);
            *gpfdat |= (val&0x1)<<5;
            break;
        case 3:
            *gpfdat &= ~(1<<6);
            *gpfdat |= (val&0x1)<<6;
            break;
    }
}




struct file_operations led_fops={
    .owner = THIS_MODULE,
    .open = led_open,
    .write  = led_write,

};

int major;
static int led_init(void)
{
    int minor;
    major = register_chrdev( 0,"led_drv", &led_fops );　　　　//当指定的设备号为0时，系统会自动生成一个设备号
    led_class = class_create(THIS_MODULE, "my_leds");
    if(IS_ERR(led_class))
        return PTR_ERR(led_class);

    led_class_devs[0] = class_device_create(led_class,NULL,MKDEV(major,0),NULL,"my_leds");　　//创建设备文件
    if(unlikely(IS_ERR(led_class_devs)))
        return PTR_ERR(led_class_devs);
    for( minor=1; minor<4; minor++ )
    {        
        led_class_devs[minor] = class_device_create(led_class,NULL,MKDEV(major,minor),NULL,"my_led%d",minor);
        if(unlikely(IS_ERR(led_class_devs)))
            return PTR_ERR(led_class_devs);
    }
    gpfcon = (volatile unsigned long *)ioremap(0x56000050,16);　　　　//物理地址映射为虚拟地址
    gpfdat = gpfcon + 1;　　　　　　　

    printk("led install Module\n");

    return 0;
}

static void led_exit(void)
{
    unregister_chrdev( major, "led_drv" );
    class_device_unregister(led_class_devs[0]);　　　　//注销设备文件
    class_device_unregister(led_class_devs[1]);
    class_device_unregister(led_class_devs[2]);
    class_device_unregister(led_class_devs[3]);
    class_destroy(led_class);　　　　　　　　　　　　　　//销毁类
    iounmap(gpfcon);　　　　　　　　　　　　　　　　　　　//取消物理地址映射
    printk("led Module exit\n");
}

module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");

模块的Makefile：

obj-m:=led.o
KERNELDIR:=/home/jz2440/linux-2.6.22.6
PWD:=$(shell pwd)
default:
    $(MAKE) -C $(KERNELDIR)  M=$(PWD) modules
clean:
    rm -rf *.o *.mod.c *.mod.o *.ko *.symvers

测试文件：

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

int main( int argc, char **argv )
{
    int fd;
    int val = 1;
    if(argc != 3 )
    {
        printf("please input righ data\n");
        printf("eg:/dev/my_leds <on\"off>\n");
        return 0;
    }
    fd = open(argv[1], O_RDWR);
    if(fd<0)
    {
        printf("open failed\n");
        return 0;
    }
    
    if(strcmp(argv[2],"on")==0)
    {
        val = 0;
    }
    else
    {
        val = 1;
    }
    write(fd, &val, 4);
　　 read(fd, &val,1);
    printf("led status =%d\n",val);
    return 0;

}

 完