原文連結: http://liu1227787871.blog.163.com/blog/static/20536319720128901736417/

上篇文章大概說明了驅動編寫的格式, 但是我們每次都要去先insmod驅動程式, 然後cat /proc/devices 來檢視主裝置號, 然後 mknod 建立裝置節點. 這一篇實現自動建立裝置節點功能.

Q: struct class *class_create(struct module *owner, const char *name)

A:  owner 表示類的所有者是誰, 一般都是 THIS_MODULE, 即當前模組. name表示類名

Q: class_device *class_device_create(struct class *cls, struct class_device *parent, dev_t  devt,  struct device *device, const char *fmt, ...);

A: 獲取主/次裝置號

注意在exit時要取消註冊 / 銷燬類 / 取消記憶體對映

class_device_unregister();

class_destroy();

unioremap();

驅動程式碼:

本程式使用copy_from_user來獲取應用層的資料, 通過該資料來開啟/關閉 led

#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 *firstdrv_class;
static struct class_device *firstdrv_class_dev;

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

static int first_drv_open(struct inode *inode, struct file *file)
{
	//printk("first_drv_open\n");
	/* 配置GPF4,5,6為輸出 */
	*gpfcon &= ~((0x3<<(4*2)) | (0x3<<(5*2)) | (0x3<<(6*2)));
	*gpfcon |= ((0x1<<(4*2)) | (0x1<<(5*2)) | (0x1<<(6*2)));
	return 0;
}

static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
	int val;

	//printk("first_drv_write\n");

	copy_from_user(&val, buf, count); //	copy_to_user();

	if (val == 1)
	{
		// 點燈
		*gpfdat &= ~((1<<4) | (1<<5) | (1<<6));
	}
	else
	{
		// 滅燈
		*gpfdat |= (1<<4) | (1<<5) | (1<<6);
	}
	
	return 0;
}

static struct file_operations first_drv_fops = {
    .owner  =   THIS_MODULE,    /* 這是一個巨集，推向編譯模組時自動建立的__this_module變數 */
    .open   =   first_drv_open,     
    .write  =	first_drv_write,	   
};

int major;
static int first_drv_init(void)
{
	major = register_chrdev(0, "first_drv", &first_drv_fops); // 註冊, 告訴核心

<span style="white-space:pre">	</span>firstdrv_class = class_create(THIS_MODULE, "firstdrv");//建立類

	firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, 0), NULL, "xyz"); /* /dev/xyz */

	gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
	gpfdat = gpfcon + 1;

	return 0;
}

static void first_drv_exit(void)
{
	unregister_chrdev(major, "first_drv"); // 解除安裝

<span style="white-space:pre">	</span>class_device_unregister(firstdrv_class_dev);
	class_destroy(firstdrv_class);
	iounmap(gpfcon);
}

module_init(first_drv_init);
module_exit(first_drv_exit);

MODULE_LICENSE("GPL");
 

驅動程式的makefile:

KERN_DIR = /home/cxh/arm/kernel/linux-2.6.22.6

all:
	make -C $(KERN_DIR) M=`pwd` modules 

clean:
	make -C $(KERN_DIR) M=`pwd` modules clean
	rm -rf modules.order

obj-m	+= first_drv.o

測試程式 test.c

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


int main(int argc, char **argv)
{
  int fd, val = 0;
  
  fd = open("dev/xyz", O_RDWR);
  if (fd < 0)
  {
    printf ("can't open /dev/xyz\n");
    return fd;
  }
  
  if (argc != 2)
  {
    printf ("usage: led <off | on>\n");
  }
  
  if (strcmp(argc[1], "on") == 0)
  {
    val = 1;
  }
  else
  {
    val = 0;
  }
  
  write(fd, &val, 4);
  
  return 0;
}

測試方法及現象:

將驅動make之後的 first.ko拷貝到 /usr/src/rootnfs/ 下,  鍵入 insmod,  將test.c 編譯之後拷貝到 /usr/src/rootnfs/ 下執行.  led on 或者 led off 可以開啟或者關閉led