Provided by: linux-doc-2.6.15_2.6.15-23.39_all bug

NAME

       mtrr_add - Add a memory type region

SYNOPSIS

       int mtrr_add  (unsigned long base, unsigned long size,
                       unsigned int type, char increment);

ARGUMENTS

       base   Physical base address of region

       size   Physical size of region

       type   Type of MTRR desired

       increment
              If this is true do usage counting on the region

DESCRIPTION

       Memory type region registers control the caching on newer Intel and non
       Intel  processors.  This  function allows drivers to request an MTRR is
       added.  The  details  and  hardware  specifics  of   each   processor’s
       implementation  are hidden from the caller, but nevertheless the caller
       should expect to need to provide a power of two size on  an  equivalent
       power of two boundary.

       If  the region cannot be added either because all regions are in use or
       the CPU cannot support it a negative value is returned. On success  the
       register  number for this entry is returned, but should be treated as a
       cookie only.

       On a multiprocessor machine the changes are  made  to  all  processors.
       This is required on x86 by the Intel processors.

       The available types are

        MTRR_TYPE_UNCACHABLE- No caching

        MTRR_TYPE_WRBACK- Write data back in bursts whenever

        MTRR_TYPE_WRCOMB- Write data back soon but allow bursts

        MTRR_TYPE_WRTHROUGH- Cache reads but not writes

BUGS

       Needs a quiet flag for the cases where drivers do not mind failures and
       do not wish system log messages to be sent.