/****************************************
 * USB主机与设备驱动
 * 主机侧：由底到高：USB主机控制器硬件-->
 * USB主机控制器驱动--> USB核心层 --> USB
 * 设备驱动层
 * 设备侧：UDC驱动程序、Gadget API和Gadget
 * 驱动程序
 * 逻辑组织：设备(1) <--> 配置(n)
 *           配置(1) <--> 接口(n)
 * 端点(0/n) <--> 接口(1) <--> 设置(n)
 * USB主机控制驱动：控制插入其中的USB设备
 * USB设备驱动：控制USB设备如何与主机通信
 * 标准描述符：
 * 设备描述符 usb_device_descriptor
 * 配置描述符 usb_config_descriptor
 * 接口描述符 usb_interface_descriptor
 * 端点描述符 usb_endpoint_descriptor
 * 字符串描述符 usb_string_descriptor
 * 几个重要的数据结构：hc_driver usb_hcd 
 * ohci_hcd usb_driver urb(请求块) 
 * urb的典型生命周期：
 * (1) 被一个USB设备驱动创建
 * (2) 初始化，被安排给一个特定USB设备的特定端点
 * (3) 被USB设备驱动提交给USB核心
 * (4) 提交与USB核心指定的USB主机控制器驱动
 * (5) 被USB主机控制器处理，进行一次到USB设备的传送
 * (6) 当urb完成，USB主机控制器驱动通知USB设备驱动
 *
 * probe() 和 disconnect() 这两个函数比较重要
 *         
 ********************************************/


/* 
 * USB 设备驱动实例：USB串口驱动(部分)
 *
 */
/* Driver structure we register with the USB core */
static struct usb_driver usb_serial_driver = {
	.name = "usbserial",
	.probe = usb_serial_probe,
	.disconnect = usb_serial_disconnect,
	.suspend = usb_serial_suspend,
	.resume = usb_serial_resume,
	.no_dynamic_id = 1,
}
/* USB串口设备驱动的模块加载函数 */
static int __init usb_serial_init(void)
{
	int i;
	int result;


	/* 分配tty_driver */
	usb_serial_tty_driver = alloc_tty_driver(SERIAL_TTY_MINORS);
	if(usb_serial_tty_driver)
	{
		return -ENOMEM;
	}
	/* 初始化全局变量 */
	for(i = 0; i < SERIAL_TTY_MINORS; ++i)
		serial_table[i] = NULL;


	/* 注册总线 */
	result = bus_register(&usb_serial_bus_type);
	if(result)
	{
		printk(KERN_ERR "usb-serial: %s - registering bus driver failed\n", __func__);
		goto exit_bus;
	}
	/* 初始化tty_driver */
	usb_serial_tty_driver->owner = THIS_MODULE;
	usb_serial_tty_driver->driver_name = "usbserial";
	usb_serial_tty_driver->name = 	"ttyUSB";
	usb_serial_tty_driver->major = SERIAL_TTY_MAJOR;
	usb_serial_tty_driver->minor_start = 0;
	usb_serial_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
	usb_serial_tty_driver->subtype = SERIAL_TYPE_NORMAL;
	usb_serial_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
	usb_serial_tty_driver->init_termios = tty_std_termios;
	usb_serial_tty_driver->init_termios.c_cflag = B9600 | CS8 | CREAD 
		                                          | HUPCL | CLOCAL;
	usb_serial_tty_driver->init_termios.c_ispeed = 9600;
	usb_serial_tty_driver->init_termios.c_ospeed = 9600;
	
	tty_set_operations(usb_serial_tty_driver, &serial_ops);
	/*  注册tty_driver */
	result = tty_register_driver(usb_serial_tty_driver);
	if (result) 
	{
		printk(KERN_ERR "usb-serial: %s - tty_register_driver failed\n",
						       __func__);
		goto exit_reg_driver;
	}
	/* 注册USB驱动 */
	result = usb_register(&usb_serial_driver);
	if (result < 0) 
	{
		printk(KERN_ERR "usb-serial: %s - usb_register failed\n",
								       __func__);
		goto exit_tty;
	}
	/* register the generic driver, if we should */
	result = usb_serial_generic_register(debug);
	if (result < 0) 
	{
		printk(KERN_ERR "usb-serial: %s - registering generic "
							       "driver failed\n", __func__);
		goto exit_generic;
	}


	printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_DESC "\n");


	return result;


exit_generic:
	usb_deregister(&usb_serial_driver);


exit_tty:
	tty_unregister_driver(usb_serial_tty_driver);


exit_reg_driver:
	bus_unregister(&usb_serial_bus_type);


exit_bus:
	printk(KERN_ERR "usb-serial: %s - returning with error %d\n",
								       __func__, result);
	put_tty_driver(usb_serial_tty_driver);
	return result;
}


static void __exit usb_serial_exit(void)
{
	usb_serial_console_exit();


	usb_serial_generic_deregister();


	usb_deregister(&usb_serial_driver); //注销usb_driver
	tty_unregister_driver(usb_serial_tty_driver); // 注销tty_driver
	put_tty_driver(usb_serial_tty_driver); // 减少引用计数