'\" t
.\"     Title: usb_interface_id
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: June 2017
.\"    Manual: Kernel Mode Gadget API
.\"    Source: Kernel Hackers Manual 4.11.3
.\"  Language: English
.\"
.TH "USB_INTERFACE_ID" "9" "June 2017" "Kernel Hackers Manual 4\&.11\&" "Kernel Mode Gadget API"
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.SH "NAME"
usb_interface_id \- allocate an unused interface ID
.SH "SYNOPSIS"
.HP \w'int\ usb_interface_id('u
.BI "int usb_interface_id(struct\ usb_configuration\ *\ " "config" ", struct\ usb_function\ *\ " "function" ");"
.SH "ARGUMENTS"
.PP
\fIstruct usb_configuration * config\fR
.RS 4
configuration associated with the interface
.RE
.PP
\fIstruct usb_function * function\fR
.RS 4
function handling the interface
.RE
.SH "CONTEXT"
.PP
single threaded during gadget setup
.SH "DESCRIPTION"
.PP
\fBusb_interface_id\fR
is called from usb_function\&.\fBbind\fR
callbacks to allocate new interface IDs\&. The function driver will then store that ID in interface, association, CDC union, and other descriptors\&. It will also handle any control requests targeted at that interface, particularly changing its altsetting via
\fBset_alt\fR\&. There may also be class\-specific or vendor\-specific requests to handle\&.
.PP
All interface identifier should be allocated using this routine, to ensure that for example different functions don\*(Aqt wrongly assign different meanings to the same identifier\&. Note that since interface identifiers are configuration\-specific, functions used in more than one configuration (or more than once in a given configuration) need multiple versions of the relevant descriptors\&.
.PP
Returns the interface ID which was allocated; or \-ENODEV if no more interface IDs can be allocated\&.
.SH "AUTHOR"
.PP
\fBDavid Brownell\fR <\&dbrownell@users.sourceforge.net\&>
.RS 4
Author.
.RE
.SH "COPYRIGHT"
.br