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libnvdimm, btt: update the usage section in Documentation

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Section 5 about BTT's in kernel usage was quite obsolete,
replace it with a simple 'Usage' section that describes how
to set up a BTT namespace using the 'ndctl' utility.

Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Vishal Verma 2016-05-27 12:43:45 -06:00 committed by Dan Williams
parent f02716db95
commit 0aefa05420
1 changed files with 9 additions and 19 deletions
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28
Documentation/nvdimm/btt.txt
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@ -256,28 +256,18 @@ If any of these error conditions are encountered, the arena is put into a read
only state using a flag in the info block.
5. In-kernel usage
==================
5. Usage
========
Any block driver that supports byte granularity IO to the storage may register
with the BTT. It will have to provide the rw_bytes interface in its
block_device_operations struct:
The BTT can be set up on any disk (namespace) exposed by the libnvdimm subsystem
(pmem, or blk mode). The easiest way to set up such a namespace is using the
'ndctl' utility [1]:
int (*rw_bytes)(struct gendisk *, void *, size_t, off_t, int rw);
For example, the ndctl command line to setup a btt with a 4k sector size is:
It may register with the BTT after it adds its own gendisk, using btt_init:
ndctl create-namespace -f -e namespace0.0 -m sector -l 4k
struct btt *btt_init(struct gendisk *disk, unsigned long long rawsize,
u32 lbasize, u8 uuid[], int maxlane);
See ndctl create-namespace --help for more options.
note that maxlane is the maximum amount of concurrency the driver wishes to
allow the BTT to use.
The BTT 'disk' appears as a stacked block device that grabs the underlying block
device in the O_EXCL mode.
When the driver wishes to remove the backing disk, it should similarly call
btt_fini using the same struct btt* handle that was provided to it by btt_init.
void btt_fini(struct btt *btt);
[1]: https://github.com/pmem/ndctl