USB_SET_INTERFACE(9)                      USB Core APIs                      USB_SET_INTERFACE(9)



NAME
       usb_set_interface - Makes a particular alternate setting be current

SYNOPSIS
       int usb_set_interface(struct usb_device * dev, int interface, int alternate);

ARGUMENTS
       dev
           the device whose interface is being updated

       interface
           the interface being updated

       alternate
           the setting being chosen.

CONTEXT
       !in_interrupt ()

DESCRIPTION
       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.

       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's default setting. To access such
       bandwidth, alternate interface settings must be made current.

       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.

       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).

RETURN
       Zero on success, or else the status code returned by the underlying usb_control_msg call.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                      USB_SET_INTERFACE(9)