Merge branch 'devlink-Add-support-for-region-access'

Alex Vesker says:

====================
devlink: Add support for region access

This is a proposal which will allow access to driver defined address
regions using devlink. Each device can create its supported address
regions and register them. A device which exposes a region will allow
access to it using devlink.

The suggested implementation will allow exposing regions to the user,
reading and dumping snapshots taken from different regions.
A snapshot represents a memory image of a region taken by the driver.

If a device collects a snapshot of an address region it can be later
exposed using devlink region read or dump commands.
This functionality allows for future analyses on the snapshots to be
done.

The major benefit of this support is not only to provide access to
internal address regions which were inaccessible to the user but also
to provide an additional way to debug complex error states using the
region snapshots.

Implemented commands:
$ devlink region help
$ devlink region show [ DEV/REGION ]
$ devlink region del DEV/REGION snapshot SNAPSHOT_ID
$ devlink region dump DEV/REGION [ snapshot SNAPSHOT_ID ]
$ devlink region read DEV/REGION [ snapshot SNAPSHOT_ID ]
	address ADDRESS length length

Show all of the exposed regions with region sizes:
$ devlink region show
pci/0000:00:05.0/cr-space: size 1048576 snapshot [1 2]
pci/0000:00:05.0/fw-health: size 64 snapshot [1 2]

Delete a snapshot using:
$ devlink region del pci/0000:00:05.0/cr-space snapshot 1

Dump a snapshot:
$ devlink region dump pci/0000:00:05.0/fw-health snapshot 1
0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30
0000000000000010 0000 0000 ffff ff04 0029 8c00 0028 8cc8
0000000000000020 0016 0bb8 0016 1720 0000 0000 c00f 3ffc
0000000000000030 bada cce5 bada cce5 bada cce5 bada cce5

Read a specific part of a snapshot:
$ devlink region read pci/0000:00:05.0/fw-health snapshot 1 address 0
	length 16
0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30

For more information you can check devlink-region.8 man page

Future:
There is a plan to extend the support to include a write command
as well as performing read and dump live region

v1->v2:
-Add a parameter to enable devlink region snapshot
-Allocate snapshot memory using kvmalloc
-Introduce destructor function devlink_snapshot_data_dest_t to avoid
 double allocation

v2->v3:
-Fix incorrect comment in devlink.h for DEVLINK_ATTR_REGION_SIZE
 from u32 to u64
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

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