inb(2)

NAME

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

SYNOPSIS

   #include <sys/io.h>

   unsigned char inb(unsigned short int port);
   unsigned char inb_p(unsigned short int port);
   unsigned short int inw(unsigned short int port);
   unsigned short int inw_p(unsigned short int port);
   unsigned int inl(unsigned short int port);
   unsigned int inl_p(unsigned short int port);

   void outb(unsigned char value, unsigned short int port);
   void outb_p(unsigned char value, unsigned short int port);
   void outw(unsigned short int value, unsigned short int port);
   void outw_p(unsigned short int value, unsigned short int port);
   void outl(unsigned int value, unsigned short int port);
   void outl_p(unsigned int value, unsigned short int port);

   void insb(unsigned short int port, void *addr,
              unsigned long int count);
   void insw(unsigned short int port, void *addr,
              unsigned long int count);
   void insl(unsigned short int port, void *addr,
              unsigned long int count);
   void outsb(unsigned short int port, const void *addr,
              unsigned long int count);
   void outsw(unsigned short int port, const void *addr,
              unsigned long int count);
   void outsl(unsigned short int port, const void *addr,
              unsigned long int count);

DESCRIPTION

   This family of functions is used to do low-level port input and output.
   The out* functions do port output, the in* functions do port input; the
   b-suffix functions are byte-width  and  the  w-suffix  functions  word-
   width; the _p-suffix functions pause until the I/O completes.

   They  are  primarily  designed for internal kernel use, but can be used
   from user space.

   You must compile with -O or -O2 or similar.  The functions are  defined
   as  inline  macros, and will not be substituted in without optimization
   enabled, causing unresolved references at link time.

   You use ioperm(2) or alternatively iopl(2) to tell the kernel to  allow
   the  user  space  application  to  access  the  I/O  ports in question.
   Failure to do this will cause the application to receive a segmentation
   fault.

CONFORMING TO

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

SEE ALSO

   ioperm(2), iopl(2)

COLOPHON

   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at
   https://www.kernel.org/doc/man-pages/.

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