LXR linux/include/asm-generic/ioctl.h

   1#ifndef _ASM_GENERIC_IOCTL_H
   2#define _ASM_GENERIC_IOCTL_H
   3
   4/* ioctl command encoding: 32 bits total, command in lower 16 bits,
   5 * size of the parameter structure in the lower 14 bits of the
   6 * upper 16 bits.
   7 * Encoding the size of the parameter structure in the ioctl request
   8 * is useful for catching programs compiled with old versions
   9 * and to avoid overwriting user space outside the user buffer area.
  10 * The highest 2 bits are reserved for indicating the ``access mode''.
  11 * NOTE: This limits the max parameter size to 16kB -1 !
  12 */
  13
  14/*
  15 * The following is for compatibility across the various Linux
  16 * platforms.  The generic ioctl numbering scheme doesn't really enforce
  17 * a type field.  De facto, however, the top 8 bits of the lower 16
  18 * bits are indeed used as a type field, so we might just as well make
  19 * this explicit here.  Please be sure to use the decoding macros
  20 * below from now on.
  21 */
  22#define _IOC_NRBITS     8
  23#define _IOC_TYPEBITS   8
  24#define _IOC_SIZEBITS   14
  25#define _IOC_DIRBITS    2
  26
  27#define _IOC_NRMASK     ((1 << _IOC_NRBITS)-1)
  28#define _IOC_TYPEMASK   ((1 << _IOC_TYPEBITS)-1)
  29#define _IOC_SIZEMASK   ((1 << _IOC_SIZEBITS)-1)
  30#define _IOC_DIRMASK    ((1 << _IOC_DIRBITS)-1)
  31
  32#define _IOC_NRSHIFT    0
  33#define _IOC_TYPESHIFT  (_IOC_NRSHIFT+_IOC_NRBITS)
  34#define _IOC_SIZESHIFT  (_IOC_TYPESHIFT+_IOC_TYPEBITS)
  35#define _IOC_DIRSHIFT   (_IOC_SIZESHIFT+_IOC_SIZEBITS)
  36
  37/*
  38 * Direction bits.
  39 */
  40#define _IOC_NONE       0U
  41#define _IOC_WRITE      1U
  42#define _IOC_READ       2U
  43
  44#define _IOC(dir,type,nr,size) \
  45        (((dir)  << _IOC_DIRSHIFT) | \
  46         ((type) << _IOC_TYPESHIFT) | \
  47         ((nr)   << _IOC_NRSHIFT) | \
  48         ((size) << _IOC_SIZESHIFT))
  49
  50/* provoke compile error for invalid uses of size argument */
  51extern unsigned int __invalid_size_argument_for_IOC;
  52#define _IOC_TYPECHECK(t) \
  53        ((sizeof(t) == sizeof(t[1]) && \
  54          sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
  55          sizeof(t) : __invalid_size_argument_for_IOC)
  56
  57/* used to create numbers */
  58#define _IO(type,nr)            _IOC(_IOC_NONE,(type),(nr),0)
  59#define _IOR(type,nr,size)      _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
  60#define _IOW(type,nr,size)      _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
  61#define _IOWR(type,nr,size)     _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
  62#define _IOR_BAD(type,nr,size)  _IOC(_IOC_READ,(type),(nr),sizeof(size))
  63#define _IOW_BAD(type,nr,size)  _IOC(_IOC_WRITE,(type),(nr),sizeof(size))
  64#define _IOWR_BAD(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))
  65
  66/* used to decode ioctl numbers.. */
  67#define _IOC_DIR(nr)            (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)
  68#define _IOC_TYPE(nr)           (((nr) >> _IOC_TYPESHIFT) & _IOC_TYPEMASK)
  69#define _IOC_NR(nr)             (((nr) >> _IOC_NRSHIFT) & _IOC_NRMASK)
  70#define _IOC_SIZE(nr)           (((nr) >> _IOC_SIZESHIFT) & _IOC_SIZEMASK)
  71
  72/* ...and for the drivers/sound files... */
  73
  74#define IOC_IN          (_IOC_WRITE << _IOC_DIRSHIFT)
  75#define IOC_OUT         (_IOC_READ << _IOC_DIRSHIFT)
  76#define IOC_INOUT       ((_IOC_WRITE|_IOC_READ) << _IOC_DIRSHIFT)
  77#define IOCSIZE_MASK    (_IOC_SIZEMASK << _IOC_SIZESHIFT)
  78#define IOCSIZE_SHIFT   (_IOC_SIZESHIFT)
  79
  80#endif /* _ASM_GENERIC_IOCTL_H */
  81