usb储存之BOT/UAS内核驱动

usb储存驱动

概览

BOT和UAS(UASP)的区别：

Windows NT内核/Linux内核都是如此的设计：
用一个标志表示UAS启用与否，用4EP支持UAS，用2EP支持BOT，判断主控是否支持STREAM，如果支持就会尝试ALT模式来使用UAS协议。
Windows NT内核驱动判断只有在高于全速2.0的情况下才会尝试UAS。

BOT仅单线程，使用2个EP:Data-In/Data-Out管道，是单工等待的，所以在高速下有瓶颈，这也是USB储存没跑满的原因。

UAS多管道（ITr/ITc/OTr/Otc）四路传输管道+USB2/USB3管道+UAS信息单元管道
一般是4个EP：datain dataout cmd status

UAS基于SCSI

声明

drivers/usb/storage/usb.c

static struct usb_driver usb_storage_driver = {
	.name =		DRV_NAME,
	.probe =	storage_probe, //这里是挂载
	.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,
};

// 这里是usb主机储存控制器的驱动模板挂载
module_usb_stor_driver(usb_storage_driver, usb_stor_host_template, DRV_NAME);

普通BOT挂载流程

如果为UAS或非常规设备，则退出storage_probe。

drivers/usb/storage/usual-tables.c 的两个数组列表

• 非规设备 ignore_ids[]
• UAS列表 usb_storage_usb_ids[]

UAS判断：uas_use_uas_driver

	/* 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

非规设备判断：

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

然后就会走usb_stor_probe1和usb_stor_probe2流程

在usb_stor_probe1里面会有协议选择，根据协议切换读写处理函数

	/* Get standard transport and protocol settings */
	get_transport(us);
	get_protocol(us);

流式UAS挂载

drivers/usb/storage/uas.c

XHCI驱动重载

主要用于重写公版驱动行为

static const struct xhci_driver_overrides xhci_pci_overrides __initconst = {
	.reset = xhci_pci_setup,
	.update_hub_device = xhci_pci_update_hub_device,
};

//init
xhci_init_driver(&xhci_pci_hc_driver, &xhci_pci_overrides);

原理：非null时重新赋值函数指针

XHCI协议spec

https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/extensible-host-controler-interface-usb-xhci.pdf

USB储存 BOT(Bulk-Only Transport)CBW-UFI命令数据流

例子：https://www.usbzh.com/tool/bot-cbw-ufi-csw.html

SCSI协议

希捷：https://www.seagate.com/files/staticfiles/support/docs/manual/Interface manuals/100293068j.pdf

其模型称为 SCSI architectural model (SAM)

CHIP 之 UASP IP

https://www.synopsys.com/blogs/chip-design/uasp-faster-usb-mass-storage.html

Others

sd 1:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

• FUA: Force Unit Access
• DPO: Disable Page Out

编写kprobe/kretprobe钩子

查看当前内核里相关的函数符号

grep uas /proc/kallsyms                                                        <

uas开头的符号有

0000000000000000 t uas_probe
0000000000000000 t uas_disconnect
0000000000000000 t uas_suspend
0000000000000000 t uas_resume
0000000000000000 t uas_reset_resume
0000000000000000 t uas_pre_reset
0000000000000000 t uas_post_reset
0000000000000000 t uas_shutdown
0000000000000000 t uas_do_work
0000000000000000 t uas_scan_work
0000000000000000 t uas_configure_endpoints
0000000000000000 t uas_queuecommand
0000000000000000 t uas_eh_abort_handler
0000000000000000 t uas_eh_device_reset_handler
0000000000000000 t uas_slave_alloc
0000000000000000 t uas_slave_configure
0000000000000000 t uas_target_alloc
0000000000000000 t uas_submit_urbs
0000000000000000 t uas_log_cmd_state
0000000000000000 t uas_stat_cmplt
0000000000000000 t uas_sense
0000000000000000 t uas_try_complete
0000000000000000 t uas_xfer_data
0000000000000000 t uas_evaluate_response_iu
0000000000000000 t uas_data_cmplt
0000000000000000 t uas_cmd_cmplt
0000000000000000 t uas_zap_pending
0000000000000000 t uas_wait_for_pending_cmnds
0000000000000000 t uas_init
0000000000000000 t uas_exit
0000000000000000 d __initcall__kmod_uas__452_1275_uas_init6
0000000000000000 d uas_driver
0000000000000000 d uas_usb_ids
0000000000000000 d uas_host_template
console:/data #

一般

查看驱动

# 看drivers段Driver=usb-storage或者uas
lsusb -t
cat /sys/kernel/usb/devices

Ref

国内现行标准：
ISO/IEC 14776-251:2014