[Python-Dev] enhanced ioctl?

[Neal Becker]

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)