'\" t
.\"     Title: usb_set_interface
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: USB Core APIs
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "USB_SET_INTERFACE" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "USB Core APIs"
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.SH "NAME"
usb_set_interface \- Makes a particular alternate setting be current
.SH "SYNOPSIS"
.HP \w'int\ usb_set_interface('u
.BI "int usb_set_interface(struct\ usb_device\ *\ " "dev" ", int\ " "interface" ", int\ " "alternate" ");"
.SH "ARGUMENTS"
.PP
\fIdev\fR
.RS 4
the device whose interface is being updated
.RE
.PP
\fIinterface\fR
.RS 4
the interface being updated
.RE
.PP
\fIalternate\fR
.RS 4
the setting being chosen\&.
.RE
.SH "CONTEXT"
.PP
!in_interrupt ()
.SH "DESCRIPTION"
.PP
This is used to enable data transfers on interfaces that may not be enabled by default\&. Not all devices support such configurability\&. Only the driver bound to an interface may change its setting\&.
.PP
Within any given configuration, each interface may have several alternative settings\&. These are often used to control levels of bandwidth consumption\&. For example, the default setting for a high speed interrupt endpoint may not send more than 64 bytes per microframe, while interrupt transfers of up to 3KBytes per microframe are legal\&. Also, isochronous endpoints may never be part of an interface\*(Aqs default setting\&. To access such bandwidth, alternate interface settings must be made current\&.
.PP
Note that in the Linux USB subsystem, bandwidth associated with an endpoint in a given alternate setting is not reserved until an URB is submitted that needs that bandwidth\&. Some other operating systems allocate bandwidth early, when a configuration is chosen\&.
.PP
This call is synchronous, and may not be used in an interrupt context\&. Also, drivers must not change altsettings while urbs are scheduled for endpoints in that interface; all such urbs must first be completed (perhaps forced by unlinking)\&.
.SH "RETURN"
.PP
Zero on success, or else the status code returned by the underlying
\fBusb_control_msg\fR
call\&.
.SH "COPYRIGHT"
.br