Linux Devlink Documentation¶

devlink is an API to expose device information and resources not directly related to any device class, such as chip-wide/switch-ASIC-wide configuration.

Locking¶

Driver facing APIs are currently transitioning to allow more explicit locking. Drivers can use the existing devlink_* set of APIs, or new APIs prefixed by devl_*. The older APIs handle all the locking in devlink core, but don’t allow registration of most sub-objects once the main devlink object is itself registered. The newer devl_* APIs assume the devlink instance lock is already held. Drivers can take the instance lock by calling devl_lock(). It is also held all callbacks of devlink netlink commands.

Drivers are encouraged to use the devlink instance lock for their own needs.

Drivers need to be cautious when taking devlink instance lock and taking RTNL lock at the same time. Devlink instance lock needs to be taken first, only after that RTNL lock could be taken.

Nested instances¶

Some objects, like linecards or port functions, could have another devlink instances created underneath. In that case, drivers should make sure to respect following rules:

Lock ordering should be maintained. If driver needs to take instance lock of both nested and parent instances at the same time, devlink instance lock of the parent instance should be taken first, only then instance lock of the nested instance could be taken.

Driver should use object-specific helpers to setup the nested relationship:

devl_nested_devlink_set() - called to setup devlink -> nested devlink relationship (could be user for multiple nested instances.

devl_port_fn_devlink_set() - called to setup port function -> nested devlink relationship.

devlink_linecard_nested_dl_set() - called to setup linecard -> nested devlink relationship.

The nested devlink info is exposed to the userspace over object-specific attributes of devlink netlink.

Interface documentation¶

The following pages describe various interfaces available through devlink in general.

Driver-specific documentation¶

Each driver that implements devlink is expected to document what parameters, info versions, and other features it supports.