1OUTB(2)                    Linux Programmer's Manual                   OUTB(2)
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NAME

6       outb, outw, outl, outsb, outsw, outsl, inb, inw, inl, insb, insw, insl,
7       outb_p, outw_p, outl_p, inb_p, inw_p, inl_p - port I/O
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SYNOPSIS

10       #include <sys/io.h>
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12       unsigned char inb(unsigned short int port);
13       unsigned char inb_p(unsigned short int port);
14       unsigned short int inw(unsigned short int port);
15       unsigned short int inw_p(unsigned short int port);
16       unsigned int inl(unsigned short int port);
17       unsigned int inl_p(unsigned short int port);
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19       void outb(unsigned char value, unsigned short int port);
20       void outb_p(unsigned char value, unsigned short int port);
21       void outw(unsigned short int value, unsigned short int port);
22       void outw_p(unsigned short int value, unsigned short int port);
23       void outl(unsigned int value, unsigned short int port);
24       void outl_p(unsigned int value, unsigned short int port);
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26       void insb(unsigned short int port, void *addr,
27                  unsigned long int count);
28       void insw(unsigned short int port, void *addr,
29                  unsigned long int count);
30       void insl(unsigned short int port, void *addr,
31                  unsigned long int count);
32       void outsb(unsigned short int port, const void *addr,
33                  unsigned long int count);
34       void outsw(unsigned short int port, const void *addr,
35                  unsigned long int count);
36       void outsl(unsigned short int port, const void *addr,
37                  unsigned long int count);
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DESCRIPTION

40       This family of functions is used to do low-level port input and output.
41       The out* functions do port output, the in* functions do port input; the
42       b-suffix functions are byte-width  and  the  w-suffix  functions  word-
43       width; the _p-suffix functions pause until the I/O completes.
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45       They  are  primarily  designed for internal kernel use, but can be used
46       from user space.
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48       You must compile with -O or -O2 or similar.  The functions are  defined
49       as  inline  macros, and will not be substituted in without optimization
50       enabled, causing unresolved references at link time.
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52       You use ioperm(2) or alternatively iopl(2) to tell the kernel to  allow
53       the  user space application to access the I/O ports in question.  Fail‐
54       ure to do this will cause the application  to  receive  a  segmentation
55       fault.
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CONFORMING TO

58       outb() and friends are hardware-specific.  The value argument is passed
59       first and the port argument is passed second,  which  is  the  opposite
60       order from most DOS implementations.
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SEE ALSO

63       ioperm(2), iopl(2)
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COLOPHON

66       This  page  is  part of release 4.15 of the Linux man-pages project.  A
67       description of the project, information about reporting bugs,  and  the
68       latest     version     of     this    page,    can    be    found    at
69       https://www.kernel.org/doc/man-pages/.
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73Linux                             2017-09-15                           OUTB(2)
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