1.. SPDX-License-Identifier: GPL-2.0
2
3==============
4Devlink Region
5==============
6
7``devlink`` regions enable access to driver defined address regions using
8devlink.
9
10Each device can create and register its own supported address regions. The
11region can then be accessed via the devlink region interface.
12
13Region snapshots are collected by the driver, and can be accessed via read
14or dump commands. This allows future analysis on the created snapshots.
15Regions may optionally support triggering snapshots on demand.
16
17Snapshot identifiers are scoped to the devlink instance, not a region.
18All snapshots with the same snapshot id within a devlink instance
19correspond to the same event.
20
21The major benefit to creating a region is to provide access to internal
22address regions that are otherwise inaccessible to the user.
23
24Regions may also be used to provide an additional way to debug complex error
25states, but see also Documentation/networking/devlink/devlink-health.rst
26
27Regions may optionally support capturing a snapshot on demand via the
28``DEVLINK_CMD_REGION_NEW`` netlink message. A driver wishing to allow
29requested snapshots must implement the ``.snapshot`` callback for the region
30in its ``devlink_region_ops`` structure. If snapshot id is not set in
31the ``DEVLINK_CMD_REGION_NEW`` request kernel will allocate one and send
32the snapshot information to user space.
33
34Regions may optionally allow directly reading from their contents without a
35snapshot. Direct read requests are not atomic. In particular a read request
36of size 256 bytes or larger will be split into multiple chunks. If atomic
37access is required, use a snapshot. A driver wishing to enable this for a
38region should implement the ``.read`` callback in the ``devlink_region_ops``
39structure. User space can request a direct read by using the
40``DEVLINK_ATTR_REGION_DIRECT`` attribute instead of specifying a snapshot
41id.
42
43example usage
44-------------
45
46.. code:: shell
47
48    $ devlink region help
49    $ devlink region show [ DEV/REGION ]
50    $ devlink region del DEV/REGION snapshot SNAPSHOT_ID
51    $ devlink region dump DEV/REGION [ snapshot SNAPSHOT_ID ]
52    $ devlink region read DEV/REGION [ snapshot SNAPSHOT_ID ] address ADDRESS length length
53
54    # Show all of the exposed regions with region sizes:
55    $ devlink region show
56    pci/0000:00:05.0/cr-space: size 1048576 snapshot [1 2] max 8
57    pci/0000:00:05.0/fw-health: size 64 snapshot [1 2] max 8
58
59    # Delete a snapshot using:
60    $ devlink region del pci/0000:00:05.0/cr-space snapshot 1
61
62    # Request an immediate snapshot, if supported by the region
63    $ devlink region new pci/0000:00:05.0/cr-space
64    pci/0000:00:05.0/cr-space: snapshot 5
65
66    # Dump a snapshot:
67    $ devlink region dump pci/0000:00:05.0/fw-health snapshot 1
68    0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30
69    0000000000000010 0000 0000 ffff ff04 0029 8c00 0028 8cc8
70    0000000000000020 0016 0bb8 0016 1720 0000 0000 c00f 3ffc
71    0000000000000030 bada cce5 bada cce5 bada cce5 bada cce5
72
73    # Read a specific part of a snapshot:
74    $ devlink region read pci/0000:00:05.0/fw-health snapshot 1 address 0 length 16
75    0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30
76
77    # Read from the region without a snapshot
78    $ devlink region read pci/0000:00:05.0/fw-health address 16 length 16
79    0000000000000010 0000 0000 ffff ff04 0029 8c00 0028 8cc8
80
81As regions are likely very device or driver specific, no generic regions are
82defined. See the driver-specific documentation files for information on the
83specific regions a driver supports.
84