linux/include/asm-generic/ioctl.h
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   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
  25/*
  26 * Let any architecture override either of the following before
  27 * including this file.
  28 */
  29
  30#ifndef _IOC_SIZEBITS
  31# define _IOC_SIZEBITS  14
  32#endif
  33
  34#ifndef _IOC_DIRBITS
  35# define _IOC_DIRBITS   2
  36#endif
  37
  38#define _IOC_NRMASK     ((1 << _IOC_NRBITS)-1)
  39#define _IOC_TYPEMASK   ((1 << _IOC_TYPEBITS)-1)
  40#define _IOC_SIZEMASK   ((1 << _IOC_SIZEBITS)-1)
  41#define _IOC_DIRMASK    ((1 << _IOC_DIRBITS)-1)
  42
  43#define _IOC_NRSHIFT    0
  44#define _IOC_TYPESHIFT  (_IOC_NRSHIFT+_IOC_NRBITS)
  45#define _IOC_SIZESHIFT  (_IOC_TYPESHIFT+_IOC_TYPEBITS)
  46#define _IOC_DIRSHIFT   (_IOC_SIZESHIFT+_IOC_SIZEBITS)
  47
  48/*
  49 * Direction bits, which any architecture can choose to override
  50 * before including this file.
  51 */
  52
  53#ifndef _IOC_NONE
  54# define _IOC_NONE      0U
  55#endif
  56
  57#ifndef _IOC_WRITE
  58# define _IOC_WRITE     1U
  59#endif
  60
  61#ifndef _IOC_READ
  62# define _IOC_READ      2U
  63#endif
  64
  65#define _IOC(dir,type,nr,size) \
  66        (((dir)  << _IOC_DIRSHIFT) | \
  67         ((type) << _IOC_TYPESHIFT) | \
  68         ((nr)   << _IOC_NRSHIFT) | \
  69         ((size) << _IOC_SIZESHIFT))
  70
  71#ifdef __KERNEL__
  72/* provoke compile error for invalid uses of size argument */
  73extern unsigned int __invalid_size_argument_for_IOC;
  74#define _IOC_TYPECHECK(t) \
  75        ((sizeof(t) == sizeof(t[1]) && \
  76          sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
  77          sizeof(t) : __invalid_size_argument_for_IOC)
  78#else
  79#define _IOC_TYPECHECK(t) (sizeof(t))
  80#endif
  81
  82/* used to create numbers */
  83#define _IO(type,nr)            _IOC(_IOC_NONE,(type),(nr),0)
  84#define _IOR(type,nr,size)      _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
  85#define _IOW(type,nr,size)      _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
  86#define _IOWR(type,nr,size)     _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
  87#define _IOR_BAD(type,nr,size)  _IOC(_IOC_READ,(type),(nr),sizeof(size))
  88#define _IOW_BAD(type,nr,size)  _IOC(_IOC_WRITE,(type),(nr),sizeof(size))
  89#define _IOWR_BAD(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))
  90
  91/* used to decode ioctl numbers.. */
  92#define _IOC_DIR(nr)            (((nr) >> _IOC_DIRSHIFT) & _IOC_DIRMASK)
  93#define _IOC_TYPE(nr)           (((nr) >> _IOC_TYPESHIFT) & _IOC_TYPEMASK)
  94#define _IOC_NR(nr)             (((nr) >> _IOC_NRSHIFT) & _IOC_NRMASK)
  95#define _IOC_SIZE(nr)           (((nr) >> _IOC_SIZESHIFT) & _IOC_SIZEMASK)
  96
  97/* ...and for the drivers/sound files... */
  98
  99#define IOC_IN          (_IOC_WRITE << _IOC_DIRSHIFT)
 100#define IOC_OUT         (_IOC_READ << _IOC_DIRSHIFT)
 101#define IOC_INOUT       ((_IOC_WRITE|_IOC_READ) << _IOC_DIRSHIFT)
 102#define IOCSIZE_MASK    (_IOC_SIZEMASK << _IOC_SIZESHIFT)
 103#define IOCSIZE_SHIFT   (_IOC_SIZESHIFT)
 104
 105#endif /* _ASM_GENERIC_IOCTL_H */
 106
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