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usb_make_path(9) [centos man page]

USB_MAKE_PATH(9)					  Host-Side Data Types and Macro					  USB_MAKE_PATH(9)

usb_make_path - returns stable device path in the usb tree SYNOPSIS
int usb_make_path(struct usb_device * dev, char * buf, size_t size); ARGUMENTS
dev the device whose path is being constructed buf where to put the string size how big is "buf"? RETURN
Length of the string (> 0) or negative if size was too small. NOTE
This identifier is intended to be "stable", reflecting physical paths in hardware such as physical bus addresses for host controllers or ports on USB hubs. That makes it stay the same until systems are physically reconfigured, by re-cabling a tree of USB devices or by moving USB host controllers. Adding and removing devices, including virtual root hubs in host controller driver modules, does not change these path identifiers; neither does rebooting or re-enumerating. These are more useful identifiers than changeable ("unstable") ones like bus numbers or device addresses. With a partial exception for devices connected to USB 2.0 root hubs, these identifiers are also predictable. So long as the device tree isn't changed, plugging any USB device into a given hub port always gives it the same path. Because of the use of "companion" controllers, devices connected to ports on USB 2.0 root hubs (EHCI host controllers) will get one path ID if they are high speed, and a different one if they are full or low speed. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 USB_MAKE_PATH(9)

Check Out this Related Man Page

EHCI(4) 						   BSD Kernel Interfaces Manual 						   EHCI(4)

ehci -- USB Enhanced Host Controller driver SYNOPSIS
ehci* at cardbus? function ? ehci* at pci? dev ? function ? usb* at ehci? DESCRIPTION
The ehci driver provides support for the USB Enhanced Host Controller Interface, which is used by USB 2.0 controllers. EHCI controllers are peculiar in that they can only handle the USB 2.0 protocol. This means that they normally have one or more companion controllers (i.e., ohci(4) or uhci(4)) handling USB 1.x devices. Consequently each USB connector is electrically connected to two USB con- trollers. The handling of this is totally automatic, but can be noticed since USB 1.x and USB 2.0 devices plugged in to the same connector appear to connect to different USB busses. SEE ALSO
cardbus(4), ohci(4), pci(4), uhci(4), usb(4) HISTORY
The ehci driver appeared in NetBSD 1.6. BUGS
The support for hubs that are connected with high speed upstream and low or full speed downstream (i.e., for transaction translators) is lim- ited. BSD
Aug 10, 2008 BSD
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