MTRR_ADD(9)							Hardware Interfaces						       MTRR_ADD(9)

NAME

       mtrr_add - Add a memory type region

SYNOPSIS

       int mtrr_add(unsigned long base, unsigned long size, unsigned int type, bool 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.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							       MTRR_ADD(9)