USB驱动之U盘驱动

Posted 2022-03-30 四季帆

        U盘使用的是drivers/usb/storage/usb.c驱动

#define DRV_NAME "usb-storage"
//插入U盘时一般会打印usb-storage 1-1:1.0: USB Mass Storage device detected
static struct usb_driver usb_storage_driver = 
	.name =		DRV_NAME,
	.probe =	storage_probe,
	.disconnect =	usb_stor_disconnect,
	.suspend =	usb_stor_suspend,
	.resume =	usb_stor_resume,
	.reset_resume =	usb_stor_reset_resume,
	.pre_reset =	usb_stor_pre_reset,
	.post_reset =	usb_stor_post_reset,
	.id_table =	usb_storage_usb_ids,
	.supports_autosuspend = 1,
	.soft_unbind =	1,
;
module_usb_stor_driver(usb_storage_driver, usb_stor_host_template, DRV_NAME);

/* The main probe routine for standard devices */
static int storage_probe(struct usb_interface *intf,
			 const struct usb_device_id *id)

	struct us_unusual_dev *unusual_dev;
	struct us_data *us;
	int result;
	int size;

	/* If uas is enabled and this device can do uas then ignore it. */
#if IS_ENABLED(CONFIG_USB_UAS)
	if (uas_use_uas_driver(intf, id, NULL))
		return -ENXIO;
#endif

	/*
	 * If the device isn't standard (is handled by a subdriver
	 * module) then don't accept it.
	 */
	if (usb_usual_ignore_device(intf)) //检测匹配
		return -ENXIO;

	/*
	 * Call the general probe procedures.
	 *
	 * The unusual_dev_list array is parallel to the usb_storage_usb_ids
	 * table, so we use the index of the id entry to find the
	 * corresponding unusual_devs entry.
	 */

	size = ARRAY_SIZE(us_unusual_dev_list);
	if (id >= usb_storage_usb_ids && id < usb_storage_usb_ids + size) 
		unusual_dev = (id - usb_storage_usb_ids) + us_unusual_dev_list;
	 else 
		unusual_dev = &for_dynamic_ids;

		dev_dbg(&intf->dev, "Use Bulk-Only transport with the Transparent SCSI protocol for dynamic id: 0x%04x 0x%04x\\n",
			id->idVendor, id->idProduct);
	

	result = usb_stor_probe1(&us, intf, id, unusual_dev,
				 &usb_stor_host_template);//probe的第一部分
	if (result)
		return result;

	/* No special transport or protocol settings in the main module */

	result = usb_stor_probe2(us);//probe的第二部分
	return result;


/* First part of general USB mass-storage probing */
int usb_stor_probe1(struct us_data **pus,
		struct usb_interface *intf,
		const struct usb_device_id *id,
		struct us_unusual_dev *unusual_dev,
		struct scsi_host_template *sht)

	struct Scsi_Host *host;
	struct us_data *us;
	int result;

	dev_info(&intf->dev, "USB Mass Storage device detected\\n");

	/*
	 * Ask the SCSI layer to allocate a host structure, with extra
	 * space at the end for our private us_data structure.
	 */
	host = scsi_host_alloc(sht, sizeof(*us));//分配Scsi_Host结构体
	if (!host) 
		dev_warn(&intf->dev, "Unable to allocate the scsi host\\n");
		return -ENOMEM;
	

	/*
	 * Allow 16-byte CDBs and thus > 2TB
	 */
	host->max_cmd_len = 16;
	host->sg_tablesize = usb_stor_sg_tablesize(intf);
	*pus = us = host_to_us(host);//从host结构体中提取出us_data结构体
	mutex_init(&(us->dev_mutex));
	us_set_lock_class(&us->dev_mutex, intf);
	init_completion(&us->cmnd_ready);//初始化完成量
	init_completion(&(us->notify));
	init_waitqueue_head(&us->delay_wait);//初始化等待队列头
	INIT_DELAYED_WORK(&us->scan_dwork, usb_stor_scan_dwork);

	/* Associate the us_data structure with the USB device */
	result = associate_dev(us, intf);//将us_data与USB设备相关联
	if (result)
		goto BadDevice;

	/* Get the unusual_devs entries and the descriptors */
	result = get_device_info(us, id, unusual_dev);//获取设备信息
	if (result)
		goto BadDevice;

	/* Get standard transport and protocol settings */
	get_transport(us);//获取传输方式
	get_protocol(us);//获取传输协议

	/*
	 * Give the caller a chance to fill in specialized transport
	 * or protocol settings.
	 */
	return 0;

BadDevice:
	usb_stor_dbg(us, "storage_probe() failed\\n");
	release_everything(us);
	return result;


/* Second part of general USB mass-storage probing */
int usb_stor_probe2(struct us_data *us)

	int result;
	struct device *dev = &us->pusb_intf->dev;

	/* Make sure the transport and protocol have both been set */
	if (!us->transport || !us->proto_handler) 
		result = -ENXIO;
		goto BadDevice;
	
	usb_stor_dbg(us, "Transport: %s\\n", us->transport_name);
	usb_stor_dbg(us, "Protocol: %s\\n", us->protocol_name);

	if (us->fflags & US_FL_SCM_MULT_TARG) 
		/*
		 * SCM eUSCSI bridge devices can have different numbers
		 * of LUNs on different targets; allow all to be probed.
		 */
		us->max_lun = 7;
		/* The eUSCSI itself has ID 7, so avoid scanning that */
		us_to_host(us)->this_id = 7;
		/* max_id is 8 initially, so no need to set it here */
	 else 
		/* In the normal case there is only a single target */
		us_to_host(us)->max_id = 1;
		/*
		 * Like Windows, we won't store the LUN bits in CDB[1] for
		 * SCSI-2 devices using the Bulk-Only transport (even though
		 * this violates the SCSI spec).
		 */
		if (us->transport == usb_stor_Bulk_transport)
			us_to_host(us)->no_scsi2_lun_in_cdb = 1;
	

	/* fix for single-lun devices */
	if (us->fflags & US_FL_SINGLE_LUN)
		us->max_lun = 0;

	/* Find the endpoints and calculate pipe values */
	result = get_pipes(us);//获得管道
	if (result)
		goto BadDevice;

	/*
	 * If the device returns invalid data for the first READ(10)
	 * command, indicate the command should be retried.
	 */
	if (us->fflags & US_FL_INITIAL_READ10)
		set_bit(US_FLIDX_REDO_READ10, &us->dflags);

	/* Acquire all the other resources and add the host */
	result = usb_stor_acquire_resources(us);//获取资源
	if (result)
		goto BadDevice;
	usb_autopm_get_interface_no_resume(us->pusb_intf);
	snprintf(us->scsi_name, sizeof(us->scsi_name), "usb-storage %s",
					dev_name(&us->pusb_intf->dev));
	result = scsi_add_host(us_to_host(us), dev);//添加scsi
	if (result) 
		dev_warn(dev,
				"Unable to add the scsi host\\n");
		goto HostAddErr;
	

	/* Submit the delayed_work for SCSI-device scanning */
	set_bit(US_FLIDX_SCAN_PENDING, &us->dflags);

	if (delay_use > 0) //delay_use秒后如果U盘没拔出则继续执行，否则执行disconnect
		dev_dbg(dev, "waiting for device to settle before scanning\\n");
	queue_delayed_work(system_freezable_wq, &us->scan_dwork,
			delay_use * HZ);
	return 0;

	/* We come here if there are any problems */
HostAddErr:
	usb_autopm_put_interface_no_suspend(us->pusb_intf);
BadDevice:
	usb_stor_dbg(us, "storage_probe() failed\\n");
	release_everything(us);
	return result;

        U盘驱动程序大概就是如此，其中probe1和probe2中还设计很多细节的内容，比如端点设置、urb控制等内容，这些内容和USB协议有很大关系，过于晦涩，所以暂时不做进一步研究。