ioctl.h

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#ifndef _UAPI_ASM_GENERIC_IOCTL_H
#define _UAPI_ASM_GENERIC_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 generic 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

/*
 * Let any architecture override either of the following before
 * including this file.
 */

#ifndef _IOC_SIZEBITS
# define _IOC_SIZEBITS  14
#endif

#ifndef _IOC_DIRBITS
# define _IOC_DIRBITS   2
#endif

#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, which any architecture can choose to override
 * before including this file.
 */

#ifndef _IOC_NONE
# define _IOC_NONE  0U
#endif

#ifndef _IOC_WRITE
# define _IOC_WRITE 1U
#endif

#ifndef _IOC_READ
# define _IOC_READ  2U
#endif

#define _IOC(dir,type,nr,size) \
    (((dir)  << _IOC_DIRSHIFT) | \
     ((type) << _IOC_TYPESHIFT) | \
     ((nr)   << _IOC_NRSHIFT) | \
     ((size) << _IOC_SIZESHIFT))

#ifndef __KERNEL__
#define _IOC_TYPECHECK(t) (sizeof(t))
#endif

/* used to create numbers */
#define _IO(type,nr)        _IOC(_IOC_NONE,(type),(nr),0)
#define _IOR(type,nr,size)  _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size)))
#define _IOW(type,nr,size)  _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
#define _IOWR(type,nr,size) _IOC(_IOC_READ|_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size)))
#define _IOR_BAD(type,nr,size)  _IOC(_IOC_READ,(type),(nr),sizeof(size))
#define _IOW_BAD(type,nr,size)  _IOC(_IOC_WRITE,(type),(nr),sizeof(size))
#define _IOWR_BAD(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 /* _UAPI_ASM_GENERIC_IOCTL_H */