1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2#ifndef _ASM_GENERIC_IOCTL_H
3#define _ASM_GENERIC_IOCTL_H
4
5/* ioctl command encoding: 32 bits total, command in lower 16 bits,
6 * size of the parameter structure in the lower 14 bits of the
7 * upper 16 bits.
8 * Encoding the size of the parameter structure in the ioctl request
9 * is useful for catching programs compiled with old versions
10 * and to avoid overwriting user space outside the user buffer area.
11 * The highest 2 bits are reserved for indicating the ``access mode''.
12 * NOTE: This limits the max parameter size to 16kB -1 !
13 */
14
15/*
16 * The following is for compatibility across the various Linux
17 * platforms. The generic ioctl numbering scheme doesn't really enforce
18 * a type field. De facto, however, the top 8 bits of the lower 16
19 * bits are indeed used as a type field, so we might just as well make
20 * this explicit here. Please be sure to use the decoding macros
21 * below from now on.
22 */
23#define _IOC_NRBITS 8
24#define _IOC_TYPEBITS 8
25
26/*
27 * Let any architecture override either of the following before
28 * including this file.
29 */
30
31#ifndef _IOC_SIZEBITS
32# define _IOC_SIZEBITS 14
33#endif
34
35#ifndef _IOC_DIRBITS
36# define _IOC_DIRBITS 2
37#endif
38
39#define _IOC_NRMASK ((1 << _IOC_NRBITS)-1)
40#define _IOC_TYPEMASK ((1 << _IOC_TYPEBITS)-1)
41#define _IOC_SIZEMASK ((1 << _IOC_SIZEBITS)-1)
42#define _IOC_DIRMASK ((1 << _IOC_DIRBITS)-1)
43
44#define _IOC_NRSHIFT 0
45#define _IOC_TYPESHIFT (_IOC_NRSHIFT+_IOC_NRBITS)
46#define _IOC_SIZESHIFT (_IOC_TYPESHIFT+_IOC_TYPEBITS)
47#define _IOC_DIRSHIFT (_IOC_SIZESHIFT+_IOC_SIZEBITS)
48
49/*
50 * Direction bits, which any architecture can choose to override
51 * before including this file.
52 *
53 * NOTE: _IOC_WRITE means userland is writing and kernel is
54 * reading. _IOC_READ means userland is reading and kernel is writing.
55 */
56
57#ifndef _IOC_NONE
58# define _IOC_NONE 0U
59#endif
60
61#ifndef _IOC_WRITE
62# define _IOC_WRITE 1U
63#endif
64
65#ifndef _IOC_READ
66# define _IOC_READ 2U
67#endif
68
69#define _IOC(dir,type,nr,size) \
70 (((dir) << _IOC_DIRSHIFT) | \
71 ((type) << _IOC_TYPESHIFT) | \
72 ((nr) << _IOC_NRSHIFT) | \
73 ((size) << _IOC_SIZESHIFT))
74
75#define _IOC_TYPECHECK(t) (sizeof(t))
76
77/*
78 * Used to create numbers.
79 *
80 * NOTE: _IOW means userland is writing and kernel is reading. _IOR
81 * means userland is reading and kernel is writing.
82 */
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

source code of include/asm-generic/ioctl.h