test_led.c 和 api test_led.c 源代码读书笔记！！！

最新推荐文章于 2021-08-17 20:07:24 发布

原创最新推荐文章于 2021-08-17 20:07:24 发布 · 552 阅读

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文章标签：

#api #读书 #struct #module #file #cmd

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这篇博客主要介绍了如何使用API打开并控制LED设备，通过源代码展示了Linux内核模块`test_led.c`的实现，包括初始化、打开、释放和IO控制函数。文章涉及了GPIO设置和字符设备驱动的操作。

API:

#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>

int main(void)
{
int fd;
fd=open("dev/test_led",0);
while(1)
{
ioctl(fd,0);sleep(1);
ioctl(fd,1);sleep(1);
}
close(fd);
return 0;
}

LINUX:

#include<linux/fs.h>
#include<linux/module.h>
#include<linux/cdev.h>
#include<linux/types.h>
#include<linux/init.h>
#include<mach/regs-gpio.h>
#include<mach/hardware.h>

#define TEST_LED_MAJOR 241
#define LED_ON 0
#define LED_OFF 1

struct test_led_dev{
struct cdev cdev;
};

struct test_led_dev *test_led_devp;
int test_led_major=TEST_LED_MAJOR;

void gpio_init(void)
{
s3c2410_gpio_setpin(S3C2410_GPB5,S3C2410_GPB5_OUTP);
}

ssize_t test_led_open(struct inode *inodep,struct file *filp)
{
return 0;
}

ssize_t test_led_release(struct inode *inodep,struct file *filep)
{
return 0;
}

ssize_t test_led_ioctl(struct inode *inodep,struct file * filp,size_t cmd,loff_t arct)
{
int ret=0;
switch(cmd)
    {
    case LED_OFF:
      s3c2410_gpio_setpin(S3C2410_GPB5,1);break;
    case LED_ON:
      s3c2410_gpio_setpin(S3C2410_GPB5,0);break;
    default:
      ret=-EINVAL;break;
    }
return ret;
}

struct file_operations test_led_fops={
.owner=THIS_MODULE,
.open=test_led_open,
.release=test_led_release,
.ioctl=test_led_ioctl,
};

static void test_led_setup(struct test_led_dev *dev,int index)
{
int err;
dev_t devno=MKDEV(test_led_major,index);
cdev_init(&dev->cdev,&test_led_fops);
dev->cdev.owner=THIS_MODULE;
dev->cdev.ops=&test_led_fops;
err=cdev_add(&dev->cdev,devno,1);
if(err)printk("cdev failed /n");
else printk("cdev ok /n");
}

int test_led_init(void)
{
int ret;
dev_t devno;
if(test_led_major)
    {
      devno=MKDEV(test_led_major,0);
      ret=register_chrdev_region(devno,1,"test_led");
    }
else
   {
     ret=alloc_chrdev_region(&devno,0,1,"test_led");
     test_led_major=MAJOR(devno);
   }
if(ret<0){printk("register dev faild/n");return ret;}
else printk("register dev ok/n");
test_led_devp=kmalloc(sizeof(struct test_led_dev),GFP_KERNEL);
if(!test_led_devp){printk("malloc failed/n");return -EINVAL;}
else printk("malloc ok /n");
test_led_setup(test_led_devp,0);
gpio_init();
return 0;
}

void test_led_exit(void)
{
cdev_del(&test_led_devp->cdev);
kfree(test_led_devp);
unregister_chrdev_region(MKDEV(test_led_major,0),1);
printk("bye bye the world");
}

module_init(test_led_init);
module_exit(test_led_exit);

MODULE_LICENSE("Dual BSD/GPL");