HPUX iomap[7]

 iomap(7)                    Series 300/400 Only                    iomap(7)





 NAME
      iomap - physical address mapping

 SYNOPSIS
      #include <sys/iomap.h>

 DESCRIPTION
      The iomap mechanism allows the mapping (thus direct access) of
      physical addresses into the user process address space.  For most
      Series 300/400 computers, the physical address space begins at
      0x000000 and extends to 0xffffff.

      The special (device) files for iomap devices are character special
      files with major number 10.

      The minor number for iomap devices is of the form:

           0xAAAANN

      where AAAA is a two-byte address, and NN is a one-byte field.

      The address portion of the minor number is formed by dividing the
      physical address by 65536.  NN x 65536 is the size of the region to be
      mapped.  For example, the minor number for a device at 0x720000 that
      occupies 128 Kbytes is 0x007202.

      Access to iomap devices is controlled by file permissions set on the
      character special file.

      Multiple processes can concurrently have a single iomap device opened
      and mapped.  It is the responsibility of the processes to synchronize
      their access.

      No read() or write() system calls are supported by the iomap driver.

      The ioctl() function is used to control the iomap device.  The
      following ioctl() requests are defined in <iomap.h>:

           IOMAPMAP            Map the iomap device into user address space
                               at the location specified by the pointer to
                               which the (void **) third argument to ioctl()
                               points.  If the argument points to a variable
                               containing a null pointer, the system selects
                               an appropriate address.  ioctl() then returns
                               the user address where the device was mapped,
                               storing it at the address pointed to by the
                               third argument (see EXAMPLES below).
                               Multiple processes can concurrently have the
                               same iomap device mapped.





 Hewlett-Packard Company            - 1 -     HP-UX Release 9.0: August 1992






 iomap(7)                    Series 300/400 Only                    iomap(7)





           IOMAPUNMAP          Unmap the iomap device from the user address
                               space.

      close() shuts down the file descriptor associated with the iomap
      device.  If the close is for the last system wide open on the device,
      the iomap device is also unmapped from the user address space;
      otherwise it is left mapped into the user address space (see
      IOMAPUNMAP above).

      One shared memory descriptor (see shmget(2)) is used for each iomap
      device.  Shared memory descriptors obtained in this way are usable
      only through the iomap interface.  Consequently, attempts to access
      them through shared memory routines (see shmat(2), shmctl(2),
      shmdt(2), etc.) result in EACCES errors.

 WARNING
      Be extremely careful when creating and using iomap devices.
      Inappropriate accesses to I/O devices or RAM can result in a system
      crash.

 ERRORS
      [EINVAL]       The address field was out of range, or the ioctl
                     request was invalid.

      [ENOMEM]       Not enough memory could be allocated for the mapping.

      [ENODEV]       Read and write calls are unsupported.

      [ENXIO]        No such device at the address specified by the minor
                     number.

      [ENOSPC]       Required resources for mapping could not be allocated.

      [ENOTTY]       Inappropriate ioctl request for this device type;
                     fildes is not a file descriptor for an iomap device
                     file.

 EXAMPLES
      Consider the following code fragment:

           #include <sys/iomap.h>
               ...
           int fildes;
           void *addr;

               ...

               addr = REQUESTED_ADDRESS;
               (void) ioctl(fildes, IOMAPMAP, &addr);
               (void) printf("actual address = 0x%x\n", addr);




 Hewlett-Packard Company            - 2 -     HP-UX Release 9.0: August 1992






 iomap(7)                    Series 300/400 Only                    iomap(7)





      where fildes is an open file descriptor for the device special file
      and REQUESTED_ADDRESS is the address originally requested by the
      program.

      If addr is a null pointer, the system selects a suitable address then
      returns the selected address in addr.

      If the value in addr is not a null pointer, it is used as a specified
      address for allocating memory.  If the specified address cannot be
      used, an error is returned (see ERRORS).

 SEE ALSO
      mknod(1M).









































 Hewlett-Packard Company            - 3 -     HP-UX Release 9.0: August 1992