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 */
  51 extern 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 */