简陋字符驱动
ubuntu版本号13.10，接着上一篇hello module。
整个寒假在家没怎么看linux内核方面的东西，忘了很多东西。参考linux/drivers/char/scx200_gpio.c写了一个及其朴素的字符设备驱动
1.切换到root账户
<![CDATA[sudo su]]>
2.创建工程目录
<![CDATA[mkdir char-device
cd char-device]]>
3.源文件、Makefile文件
char-device.c
<![CDATA[#include <linux/device.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/types.h>
#include <linux/cdev.h>
MODULE_AUTHOR("mrhopehub <mrhopehub@163.com>");
MODULE_DESCRIPTION("my first char driver");
MODULE_LICENSE("GPL");
char file_private_data = 'o';
static int major = 0; /* default to dynamic major */
static int char_device_open(struct inode *inode, struct file *file)
{
file->private_data = &file_private_data;
return 0;
}
ssize_t char_device_write(struct file *file, const char __user *data,
size_t len, loff_t *ppos)
{
int i;
char c;
char *tmp = file->private_data;
char private = *tmp;
for(i=0; i<len; i++)
{
get_user(c, data + i);
if(c == private)printk("第%d个写入的字符,与私有数据相等。\n",i);
else printk("与私有数据不想等的字符：%c\n",c);
}
return len;
}
static const struct file_operations char_device_fileops = {
.owner = THIS_MODULE,
.write = char_device_write,
.open = char_device_open,
};
static struct cdev my_device_cdev;
static int __init hello_device_init(void)
{
int rc;
dev_t devid;
rc = alloc_chrdev_region(&devid, 0, 1, "my-char-device");
major = MAJOR(devid);
if(rc < 0)
{
printk("设备号分配出错！！\n");
return -1;
}
cdev_init(&my_device_cdev, &char_device_fileops);
cdev_add(&my_device_cdev, devid, 1);
printk("\n模块初始化成功！\n");
return 0;
}
static void __exit hello_device_cleanup(void)
{
cdev_del(&my_device_cdev);
unregister_chrdev_region(MKDEV(major, 0), 1);
printk("\n模块移除成功！\n");
}
module_init(hello_device_init);
module_exit(hello_device_cleanup);
]]>
Makefile文件
<![CDATA[obj-m += char-device.o
KERNELDIR := /usr/src/linux
PWD := $(shell pwd)
modules:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
modules_install:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install
clean:
$(MAKE) -C $(KERNELDIR) M=$(PWD) clean]]>
4.编译模块
<![CDATA[make]]>
5.加载模块
<![CDATA[insmod char-device.ko]]>
6.查看设备对应的主设备号
<![CDATA[cat /proc/devices]]>
7./dev目录下创建设备节点
（假设上一步看到的my-char-device的主设备号是250，系统分配，笔者主机上分配的250）
<![CDATA[mknod /dev/hello-cdev c 250 0]]>
8.测试写入函数，既写入hello-cdev文件一些字符
<![CDATA[echo oooo > /dev/hello-cdev]]>
9.查看结果
<![CDATA[cat /var/log/kern.log]]>
10.删除设备节点、卸载模块
<![CDATA[rm /dev/hello-cdev
rmmod char-device]]>
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