实验

驱动文件hello.c

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>

#define    HELLO_MAJOR     231
#define    DEVICE_NAME     "HelloModule"

static int hello_open(struct inode *inode, struct file *file){
    printk(KERN_EMERG "hello open.
");
    return 0;
}

static int hello_write(struct file *file, const char __user * buf, size_t count, loff_t *ppos){
    printk(KERN_EMERG "hello write.
");
    return 0;
}

static struct file_operations hello_flops = {
    .owner  =   THIS_MODULE,
    .open   =   hello_open,     
    .write  =   hello_write,
};

static int __init hello_init(void){
    int ret;
    
    ret = register_chrdev(HELLO_MAJOR,DEVICE_NAME, &hello_flops);
    if (ret < 0) {
      printk(KERN_EMERG DEVICE_NAME " can't register major number.
");
      return ret;
    }
    printk(KERN_EMERG DEVICE_NAME " initialized.
");
    return 0;
}

static void __exit hello_exit(void){
    unregister_chrdev(HELLO_MAJOR, DEVICE_NAME);
    printk(KERN_EMERG DEVICE_NAME " removed.
");
}

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");

编译驱动所需的Makefile

ifneq ($(KERNELRELEASE),)
MODULE_NAME = hellomodule
$(MODULE_NAME)-objs := hello.o
obj-m := $(MODULE_NAME).o
else
KERNEL_DIR = /lib/modules/`uname -r`/build
MODULEDIR := $(shell pwd)

.PHONY: modules
default: modules

modules:
    make -C $(KERNEL_DIR) M=$(MODULEDIR) modules

clean distclean:
    rm -f *.o *.mod.c .*.*.cmd *.ko
    rm -rf .tmp_versions
endif

1、编译驱动

#make

2、编译上层应用

#gcc hellotest.c -o hellotest

3、加载驱动

#insmod hellomodule.ko

insmod加载驱动的时候，会调用函数hello_init()，打印的调试信息如下。

但是在"/proc/devices"中看不到已经加载的模块。