Provided by: kernel-doc-2.4.27_2.4.27-12_all
mtrr_add - Add a memory type region
int mtrr_add (unsigned long base, unsigned long size, unsigned int
type, char increment);
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
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
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
Needs a quiet flag for the cases where drivers do not mind failures
and do not wish system log messages to be sent.