[mythtv] _IOWR Function
superm1 at gmail.com
Mon Sep 27 14:00:31 EDT 2004
In attempting to compile the frontend in windows, I'm running into a
bit of a road block, vsync.cpp in libmythTV is referring to a function
_IOWR not valid in cygwin.
>From what I have found comparing linux and cygwin header files,
vsync.cpp includes /usr/include/sys/ioctl.h which includes
/usr/includes/bits/ioctl-typesh which includes
/usr/include/asm/ioctls.h which includes /usr/include/asm/ioctl.h
which seems to be where _IOWR is defined.
/usr/include/sys/ioctl.h doesnt include any of those files, nor does
the _IOWR function exist in any files when I tried to grep for it.
Now my understanding of this function is a bit rudimentary, so could
someone explain exactly what it it used for?
#define _IOC_NRBITS 8
#define _IOC_TYPEBITS 8
#define _IOC_SIZEBITS 14
#define _IOC_DIRBITS 2
#define _IOC_NRMASK ((1 << _IOC_NRBITS)-1)
#define _IOC_TYPEMASK ((1 << _IOC_TYPEBITS)-1)
#define _IOC_SIZEMASK ((1 << _IOC_SIZEBITS)-1)
#define _IOC_DIRMASK ((1 << _IOC_DIRBITS)-1)
#define _IOC_NRSHIFT 0
#define _IOC_TYPESHIFT (_IOC_NRSHIFT+_IOC_NRBITS)
#define _IOC_SIZESHIFT (_IOC_TYPESHIFT+_IOC_TYPEBITS)
#define _IOC_DIRSHIFT (_IOC_SIZESHIFT+_IOC_SIZEBITS)
* Direction bits.
#define _IOC_NONE 0U
#define _IOC_WRITE 1U
#define _IOC_READ 2U
#define _IOC(dir,type,nr,size) \
(((dir) << _IOC_DIRSHIFT) | \
((type) << _IOC_TYPESHIFT) | \
((nr) << _IOC_NRSHIFT) | \
((size) << _IOC_SIZESHIFT))
/* used to create numbers */
#define _IO(type,nr) _IOC(_IOC_NONE,(type),(nr),0)
#define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),sizeof(size))
#define _IOW(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),sizeof(size))
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