IIUC, current ioctl is not capable of handling arbitrary argument types. This code will allow any arg type (such as structures with pointers to embedded structures).

The code for _IOC is taken from linux and might not be portable.

from ctypes import *

libc = CDLL ('/lib/libc.so.6') #print libc.ioctl

def set_ioctl_argtype (arg_type): libc.ioctl.argtypes = (c_int, c_int, arg_type)

_IOC_WRITE = 0x1

_IOC_NRBITS= 8 _IOC_TYPEBITS= 8 _IOC_SIZEBITS= 14 _IOC_DIRBITS= 2

_IOC_NRSHIFT= 0 _IOC_TYPESHIFT= (_IOC_NRSHIFT+_IOC_NRBITS) _IOC_SIZESHIFT= (_IOC_TYPESHIFT+_IOC_TYPEBITS) _IOC_DIRSHIFT= (_IOC_SIZESHIFT+_IOC_SIZEBITS)

def _IOC (dir, type, nr, size): return (((dir) << _IOC_DIRSHIFT) | \ ((type) << _IOC_TYPESHIFT) | \ ((nr) << _IOC_NRSHIFT) | \ ((size) << _IOC_SIZESHIFT))

def ioctl (fd, request, args): return libc.ioctl (fd, request, args) ------------------- Example usage:

from ioctl import *

set_ioctl_argtype (POINTER (eos_dl_args_t))

EOS_IOC_MAGIC = 0xF4 request = _IOC(_IOC_WRITE, EOS_IOC_MAGIC, 0x00, 0) # ignore size

err = ioctl (eos_file.fileno(), request, args)