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 
 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 */
 73 extern 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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