'\" t
.\"     Title: usb_make_path
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Host-Side Data Types and Macros
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "USB_MAKE_PATH" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Host-Side Data Types and Macro"
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.SH "NAME"
usb_make_path \- returns stable device path in the usb tree
.SH "SYNOPSIS"
.HP \w'int\ usb_make_path('u
.BI "int usb_make_path(struct\ usb_device\ *\ " "dev" ", char\ *\ " "buf" ", size_t\ " "size" ");"
.SH "ARGUMENTS"
.PP
\fIdev\fR
.RS 4
the device whose path is being constructed
.RE
.PP
\fIbuf\fR
.RS 4
where to put the string
.RE
.PP
\fIsize\fR
.RS 4
how big is
\(lqbuf\(rq?
.RE
.SH "RETURN"
.PP
Length of the string (> 0) or negative if size was too small\&.
.SH "NOTE"
.PP
This identifier is intended to be
\(lqstable\(rq, 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 (\(lqunstable\(rq) ones like bus numbers or device addresses\&.
.PP
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\*(Aqt changed, plugging any USB device into a given hub port always gives it the same path\&. Because of the use of
\(lqcompanion\(rq
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\&.
.SH "COPYRIGHT"
.br