1outb(2)                       System Calls 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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LIBRARY

10       Standard C library (libc, -lc)
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SYNOPSIS

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

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

61       outb() and friends are hardware-specific.  The value argument is passed
62       first and the port argument is passed second, which is the opposite or‐
63       der from most DOS implementations.
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STANDARDS

66       None.
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SEE ALSO

69       ioperm(2), iopl(2)
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73Linux man-pages 6.04              2023-03-30                           outb(2)
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