据我了解，连接到不同控制器的设备应显示在不同的 USB 总线下。但是，当我将键盘连接到 xHCI 控制器时，它仍然列在 EHCI 总线之一下。查看>>>>清单中的标记：
$ lspci | grep -i usb
>>>> 00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB xHCI (rev 04)
00:1a.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #2 (rev 04)
00:1d.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #1 (rev 04)
$ lspci -vs 00:14.0
00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB xHCI (rev 04) (prog-if 30 [XHCI])
Subsystem: ASUSTeK Computer Inc. 8 Series/C220 Series Chipset Family USB xHCI
Flags: bus master, medium devsel, latency 0, IRQ 27
Memory at ef920000 (64-bit, non-prefetchable) [size=64K]
Capabilities: [70] Power Management version 2
Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
Kernel driver in use: xhci_hcd
所以我确实有一个 xHCI 控制器。它是主板上的一个单独的物理端口。
$lsusb
Bus 002 Device 002: ID 8087:8000 Intel Corp.
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:8008 Intel Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
>>>> Bus 004 Device 002: ID 174c:3074 ASMedia Technology Inc. ASM1074 SuperSpeed hub
>>>> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 014: ID 046d:c03d Logitech, Inc. M-BT96a Pilot Optical Mouse
Bus 003 Device 015: ID 195d:2030 Itron Technology iONE
Bus 003 Device 013: ID 05e3:0608 Genesys Logic, Inc. Hub
Bus 003 Device 012: ID 0424:2228 Standard Microsystems Corp. 9-in-2 Card Reader
Bus 003 Device 011: ID 0424:2602 Standard Microsystems Corp. USB 2.0 Hub
Bus 003 Device 010: ID 0424:2512 Standard Microsystems Corp. USB 2.0 Hub
Bus 003 Device 003: ID 174c:2074 ASMedia Technology Inc. ASM1074 High-Speed hub
>>>> Bus 003 Device 016: ID 03f0:0024 Hewlett-Packard KU-0316 Keyboard
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
总线 004 上的“超高速”3.0 集线器应该是 xHCI 控制器。然而，键盘连接到总线 003：
$lsusb -t
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M
|__ Port 3: Dev 2, If 0, Class=Hub, Driver=hub/4p, 5000M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/14p, 480M
>>>>|__ Port 1: Dev 16, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
|__ Port 3: Dev 3, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 2: Dev 10, If 0, Class=Hub, Driver=hub/2p, 480M
|__ Port 1: Dev 11, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 1: Dev 12, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 3: Dev 13, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 2: Dev 15, If 0, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 2: Dev 15, If 1, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 2: Dev 15, If 2, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 4: Dev 14, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/8p, 480M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/2p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/6p, 480M
事实上，无论我如何将设备连接到物理控制器，它们总是出现在同一总线下。有谁知道可能发生了什么？
系统
Processor: Intel(R) Core(TM) i7-4771 CPU @ 3.50GHz
OS: Debian GNU/Linux testing (buster) with ACS patch, IOMMU enabled.
Kernel: Linux 4.10.0-acs+ (x86_64)
Version: #3 SMP PREEMPT Sun Feb 26 00:03:48 CET 2017
Processor: Intel(R) Core(TM) i7-4771 CPU @ 3.50GHz : 3900.00 MHz
Board: Asus Z87-PRO
BIOS: AMI version 1707, VT-d/x enabled