so2学习日志3-字符设备

设备注册/销毁入口

module_init(so2_cdev_init);
module_exit(so2_cdev_exit);

在注册函数中，进行设备的初始化，包括设备号，原子变量等

static int so2_cdev_init(void)
{
	int err;
	int i;

	/* TODO 1: register char device region for MY_MAJOR and NUM_MINORS starting at MY_MINOR */
	register_chrdev_region(MKDEV(MY_MAJOR, MY_MINOR), NUM_MINORS, MODULE_NAME);

	for (i = 0; i < NUM_MINORS; i++) {
		/*TODO 4: initialize buffer with MESSAGE string */
		strcpy(devs[i].buffer, MESSAGE);
		/* TODO 3: set access variable to 0, use atomic_set */
		atomic_set(&devs[i].access, 0);
		/* TODO 2: init and add cdev to kernel core */
		cdev_init(&devs[i].cdev, &so2_fops);
		cdev_add(&devs[i].cdev, MKDEV(MY_MAJOR, MY_MINOR + i), 1);
	}

	return 0;
}

注销函数同理

static void so2_cdev_exit(void)
{
	int i;
	for (i = 0; i < NUM_MINORS; i++) {
		/* TODO 2: delete cdev from kernel core */
		cdev_del(&devs[i].cdev);
	}
	/* TODO 1: unregister char device region, for MY_MAJOR and NUM_MINORS starting at MY_MINOR */
	unregister_chrdev_region(MKDEV(MY_MAJOR, MY_MINOR), NUM_MINORS);
}