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



NAME
       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 4.8.                 January 2017                          USB_MAKE_PATH(9)