Linux设备驱动的Hello World(2)

二、Linux系统下的LED驱动

在Linux 操作系统下编写LED 设备的驱动时，操作硬件的LightInit()、LightOn()、LightOff()这些函数仍然需要，但是，需要遵循Linux编程的命名习惯，重新将其命名为light_init()、light_on()、light_off()。这些函数将被LED 驱动中独立于设备的针对内核的接口进行调用。

led.c:

//head
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/cdev.h>

#define BASE_NUM 0
#define COUNT 1
#define DEV_NAME "led"

static char k_buf[128] = {0};
//static struct cdev *led_cdev = NULL;
static struct cdev led_cdev;
static dev_t dev = 0;
//#define VADDR __REG(0x10500000)
static volatile unsigned int pa = 0x10500000;
static volatile unsigned int va;

//description
MODULE_AUTHOR("huangminqiang2007@163.com");
MODULE_DESCRIPTION("THIS IS FOR TESTING");
MODULE_LICENSE("GPL");

//open close read write
//open
static int led_open(struct inode *i_node, struct file *filep)
{
 return 0;
}

//close
static int led_close(struct inode *i_node, struct file *filep)
{
 return 0;
}

//read
static int led_read(struct file *filep,char *buf,
   size_t size,loff_t *offset)
{
 int cnt = -1;
 
 if(NULL == filep)
 {
  goto _out;
 } 
 
 cnt = copy_to_user(buf,k_buf,sizeof(k_buf));
 
 return (sizeof(k_buf)-cnt);
_out:
 return -1;
}

//write
static int led_write(struct file *filep,const char *buf,
   size_t size,loff_t *offset)
{
 if(NULL == filep)
 {
  goto _out;
 } 

copy_from_user(k_buf,buf,size);
 *(char *)va = k_buf[0]; 
 //writew(k_buf[0],va);
 //*(char *)VADDR = k_buf[0];
 return size;
_out:
 return -1;
}

//file operations
static struct file_operations led_ops = {
 .owner=   THIS_MODULE,
 .open=  led_open,
 .release= led_close, 
 .read=   led_read,
 .write=  led_write,
};

//init
static int __init led_init(void)
{
 int cnt = -1;
 
 //paddr to vaddr
 (int *)va = ioremap(pa,4);

//alloc cdev region
 cnt = alloc_chrdev_region(&dev,BASE_NUM,COUNT,DEV_NAME);
 if(0 > cnt)
 {
  goto _out;
 }
 
 //alloc cdev，如果直接定义变量则不用申请内存。
 //led_cdev = cdev_alloc();
 //init cdev
 cdev_init(&led_cdev,&led_ops);
 //add cdev
 cnt = cdev_add(&led_cdev,dev,COUNT);
 //printk major_num
 printk("<0>" "major number : %d\n",MAJOR(dev));

 if(0 > cnt)
 {
  goto _out;
 }

printk("<0>" "init ok!\n");

return 0;
_out:
 return -1;
}

//exit
static void __exit led_exit(void)
{
 //unregister cdev region
 unregister_chrdev_region(dev,COUNT);
 //del cdev
 cdev_del(&led_cdev);

iounmap((char *)va);

printk("<0>" "exit ok!\n");
}

//add to kernel
module_init(led_init);
module_exit(led_exit);