text: /*
   *  include/asm-s390/ioctl.h
   *
   *  S390 version
   *
   *  Derived from "include/asm-i386/ioctl.h"
   */
  
  #ifndef _S390_IOCTL_H
  #define _S390_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.
   */
  #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))
  #define _IOWR(type,nr,size)	_IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))
  
  /* used to decode ioctl numbers.. */
  #define _IOC_DIR(nr)		(((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)
  #define _IOC_TYPE(nr)		(((nr) >> _IOC_TYPESHIFT) & _IOC_TYPEMASK)
  #define _IOC_NR(nr)		(((nr) >> _IOC_NRSHIFT) & _IOC_NRMASK)
  #define _IOC_SIZE(nr)		(((nr) >> _IOC_SIZESHIFT) & _IOC_SIZEMASK)
  
  /* ...and for the drivers/sound files... */
  
  #define IOC_IN		(_IOC_WRITE << _IOC_DIRSHIFT)
  #define IOC_OUT		(_IOC_READ << _IOC_DIRSHIFT)
  #define IOC_INOUT	((_IOC_WRITE|_IOC_READ) << _IOC_DIRSHIFT)
  #define IOCSIZE_MASK	(_IOC_SIZEMASK << _IOC_SIZESHIFT)
  #define IOCSIZE_SHIFT	(_IOC_SIZESHIFT)
  
  #endif /* _S390_IOCTL_H */
  