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