ioctl.py

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# -*- coding: utf-8 -*-
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# Copyright [2010-2014] Institute of Nuclear Physics PAN, Krakow, Poland
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#    you may not use this file except in compliance with the License.
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#!/usr/bin/python2.4
# vim:ts=4:sw=4:softtabstop=4:smarttab:expandtab
#
# $Id$
#
#    Copyright (C) 1999-2006  Keith Dart <keith@kdart.com>
#
#    This library is free software; you can redistribute it and/or
#    modify it under the terms of the GNU Lesser General Public
#    License as published by the Free Software Foundation; either
#    version 2.1 of the License, or (at your option) any later version.
#
#    This library is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#    Lesser General Public License for more details.

##
# 
# Linux ioctl macros. Taken from /usr/include/asm/ioctl.h
# 
# 

# ioctl command encoding: 32 bits total, command in lower 16 bits,
# size of the parameter structure in the lower 14 bits of the
# upper 16 bits.
# Encoding the size of the parameter structure in the ioctl request
# is useful for catching programs compiled with old versions
# and to avoid overwriting user space outside the user buffer area.
# The highest 2 bits are reserved for indicating the ``access mode''.
# NOTE: This limits the max parameter size to 16kB -1 !
#
#
# The following is for compatibility across the various Linux
# platforms.  The i386 ioctl numbering scheme doesn't really enforce
# a type field.  De facto, however, the top 8 bits of the lower 16
# bits are indeed used as a type field, so we might just as well make
# this explicit here.  Please be sure to use the decoding macros
# below from now on.

import struct
sizeof = struct.calcsize

_IOC_NRBITS = 8
_IOC_TYPEBITS = 8
_IOC_SIZEBITS = 14
_IOC_DIRBITS = 2
_IOC_NRMASK = ((1 << _IOC_NRBITS)-1)
_IOC_TYPEMASK = ((1 << _IOC_TYPEBITS)-1)
_IOC_SIZEMASK = ((1 << _IOC_SIZEBITS)-1)
_IOC_DIRMASK = ((1 << _IOC_DIRBITS)-1)
_IOC_NRSHIFT = 0
_IOC_TYPESHIFT = (_IOC_NRSHIFT+_IOC_NRBITS)
_IOC_SIZESHIFT = (_IOC_TYPESHIFT+_IOC_TYPEBITS)
_IOC_DIRSHIFT = (_IOC_SIZESHIFT+_IOC_SIZEBITS)

IOCSIZE_MASK = (_IOC_SIZEMASK << _IOC_SIZESHIFT)
IOCSIZE_SHIFT = (_IOC_SIZESHIFT)

###
# direction bits
_IOC_NONE = 0
_IOC_WRITE = 1
_IOC_READ = 2

def _IOC(dir,type,nr,FMT):
        return int((((dir)  << _IOC_DIRSHIFT) | \
         ((type) << _IOC_TYPESHIFT) | \
         ((nr)   << _IOC_NRSHIFT) | \
         ((FMT) << _IOC_SIZESHIFT)) & 0xffffffff )


# used to create numbers
# type is the assigned type from the kernel developers
# nr is the base ioctl number (defined by driver writer)
# FMT is a struct module format string.
def _IO(type,nr): return _IOC(_IOC_NONE,(type),(nr),0)
def _IOR(type,nr,FMT): return _IOC(_IOC_READ,(type),(nr),sizeof(FMT))
def _IOW(type,nr,FMT): return _IOC(_IOC_WRITE,(type),(nr),sizeof(FMT))
def _IOWR(type,nr,FMT): return _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(FMT))

# used to decode ioctl numbers
def _IOC_DIR(nr): return (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)
def _IOC_TYPE(nr): return (((nr) >> _IOC_TYPESHIFT) & _IOC_TYPEMASK)
def _IOC_NR(nr): return (((nr) >> _IOC_NRSHIFT) & _IOC_NRMASK)
def _IOC_SIZE(nr): return (((nr) >> _IOC_SIZESHIFT) & _IOC_SIZEMASK)