linux/Documentation/admin-guide/mm/cma_debugfs.rst
Mauro Carvalho Chehab 4f4cfa6c56 docs: admin-guide: add a series of orphaned documents
There are lots of documents that belong to the admin-guide but
are on random places (most under Documentation root dir).

Move them to the admin guide.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
2019-07-15 11:03:02 -03:00

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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 zone represents a directory under <debugfs>/cma/, indexed by the
kernel's CMA index. So the first CMA zone would be:
<debugfs>/cma/cma-0
The structure of the files created under that directory is as follows:
- [RO] base_pfn: The base PFN (Page Frame Number) of the zone.
- [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 page states in the zone.
- [WO] alloc: Allocate N pages from that CMA area. For example::
echo 5 > <debugfs>/cma/cma-2/alloc
would try to allocate 5 pages from the cma-2 area.
- [WO] free: Free N pages from that CMA area, similar to the above.