Manpages - outb.2

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

  #include <sys/io.h>

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

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

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

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.

*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.

*ioperm*(2), *iopl*(2)

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