usb_set_interface(9) - phpMan
USB_SET_INTERFACE(9) USB Core APIs USB_SET_INTERFACE(9)
usb_set_interface - Makes a particular alternate setting be current
int usb_set_interface(struct usb_device * dev, int interface, int alternate);
the device whose interface is being updated
the interface being updated
the setting being chosen.
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).
Zero on success, or else the status code returned by the underlying usb_control_msg call.
Kernel Hackers Manual 4.8. January 2017 USB_SET_INTERFACE(9)