Man page 9 : usb_altnum_to_altsetting

usb_altnum_to_altsetting - get the altsetting structure with a given alternate setting number.

struct usb_host_interface * usb_altnum_to_altsetting(const struct usb_interface *  intf , unsigned int  altnum );

intf
    the interface containing the altsetting in question

altnum
    the desired alternate setting number

This searches the altsetting array of the specified interface for an entry with the correct bAlternateSetting value and returns a pointer to that entry, or null.

Note that altsettings need not be stored sequentially by number, so it would be incorrect to assume that the first altsetting entry in the array corresponds to altsetting zero. This routine helps device drivers avoid such mistakes.

DonAqt call this function unless you are bound to the intf interface or you have locked the device!