ioctl.h

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/**
*
 $Id: ioctl.h,v 1.5 1993/07/19 21:53:50 root Exp root $
 *
 * linux/ioctl.h for Linux by H.H. Bergman.


*/

#ifndef _LINUX_IOCTL_H
#define _LINUX_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 !


*/

#define IOC_VOID        0x00000000      ///< param in size field 
#define IOC_IN          0x40000000      ///< user --> kernel 
#define IOC_OUT         0x80000000      ///< kernel --> user 
#define IOC_INOUT       (IOC_IN | IOC_OUT)      ///< both 
#define IOCSIZE_MASK    0x3fff0000      ///< size (max 16k-1 bytes) 
#define IOCSIZE_SHIFT   16              ///< how to get the size 
#define IOCCMD_MASK     0x0000ffff      ///< command code 
#define IOCCMD_SHIFT    0


/**
*
 _IO(magic, subcode); size field is zero and the 
 * subcode determines the command.


*/
#define _IO(c,d)        (IOC_VOID | ((c)<<8) | (d)) ///< param encoded 

/**
*
 _IOXX(magic, subcode, arg_t); where arg_t is the type of the
 * (last) argument field in the ioctl call, if present.


*/
#define _IOW(c,d,t)     (IOC_IN | ((sizeof(t)<<16) & IOCSIZE_MASK) | \
                                  ((c)<<8) | (d))
#define _IOR(c,d,t)     (IOC_OUT | ((sizeof(t)<<16) & IOCSIZE_MASK) | \
                                   ((c)<<8) | (d))
/// WR rather than RW to avoid conflict with stdio.h 
#define _IOWR(c,d,t)    (IOC_INOUT | ((sizeof(t)<<16) & IOCSIZE_MASK) | \
                                     ((c)<<8) | (d))

#endif // _LINUX_IOCTL_H 

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