linux - Pass param to USB ioctl -
    i have problem read/write data usb mass storage device, 'device or resource busy' error below command:   ioctl(usbfd, usbdevfs_claiminterface, &interface_num)    so need release interface before. don't know how can  pass interface_num correctly command:   ioctl(usbfd, usbdevfs_releaseinterface, &interface_num),    if it's not defined, there function found interface number. please me! thanks.          the documentation states:      usbdevfs_releaseinterface       this used release claim usbfs made on interface, either   implicitly or because of usbdevfs_claiminterface  call, before   file descriptor closed. ioctl parameter integer holding   number of interface ( binterfacenumber  descriptor); file   modification time not updated request.    but seems here "parameter integer" still means pointer integer should passed, you're showing. if have descriptor, can find interface number.