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=====================
CMA Debugfs Interface
=====================
The CMA debugfs interface is useful to retrieve basic information out of the
different CMA areas and to test allocation/release in each of the areas.
Each CMA area represents a directory under <debugfs>/cma/, represented by
its CMA name like below:
<debugfs>/cma/<cma_name>
The structure of the files created under that directory is as follows:
- [RO] base_pfn: The base PFN (Page Frame Number) of the CMA area.
This is the same as ranges/0/base_pfn.
- [RO] count: Amount of memory in the CMA area.
- [RO] order_per_bit: Order of pages represented by one bit.
- [RO] bitmap: The bitmap of allocated pages in the area.
This is the same as ranges/0/base_pfn.
- [RO] ranges/N/base_pfn: The base PFN of contiguous range N
in the CMA area.
- [RO] ranges/N/bitmap: The bit map of allocated pages in
range N in the CMA area.
- [WO] alloc: Allocate N pages from that CMA area. For example::
echo 5 > <debugfs>/cma/<cma_name>/alloc
would try to allocate 5 pages from the 'cma_name' area.
- [WO] free: Free N pages from that CMA area, similar to the above.
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