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man pages section 9: DDI and DKI Kernel Functions

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Updated: July 2017



rmfree - free space back into a resource map


#include <sys/map.h> 
#include <sys/ddi.h> 

void rmfree(struct map *mp, size_t size, ulong_t index);

Interface Level

Architecture independent level 1 (DDI/DKI).



Pointer to the map structure.


Number of units being freed.


Index of the first unit of the allocated resource.


The rmfree() function releases space back into a resource map. It is the opposite of rmalloc(9F), which allocates space that is controlled by a resource map structure.

When releasing resources using rmfree() the size and index passed to rmfree() must exactly match the size and index values passed to and returned from a previous call to rmalloc(). Resources cannot be returned piecemeal.

Drivers may define resource maps for resource allocation, in terms of arbitrary units, using the rmallocmap(9F) function. The system maintains the resource map structure by size and index, computed in units appropriate for the resource. For example, units may be byte addresses, pages of memory, or blocks. rmfree() frees up unallocated space for re-use.

The rmfree() function can also be used to initialize a resource map, in which case the size and index should cover the entire resource area.


The rmfree() function can be called from user, interrupt, or kernel context.

See Also

rmalloc(9F), rmalloc_wait(9F), rmallocmap(9F), rmfreemap(9F)

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