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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 */
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