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devlink: support default values for param-get and param-set

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Support querying and resetting to default param values.

Introduce two new devlink netlink attrs:
DEVLINK_ATTR_PARAM_VALUE_DEFAULT and
DEVLINK_ATTR_PARAM_RESET_DEFAULT. The former is used to contain an
optional parameter value inside of the param_value nested
attribute. The latter is used in param-set requests from userspace to
indicate that the driver should reset the param to its default value.

To implement this, two new functions are added to the devlink driver
api: devlink_param::get_default() and
devlink_param::reset_default(). These callbacks allow drivers to
implement default param actions for runtime and permanent cmodes. For
driverinit params, the core latches the last value set by a driver via
devl_param_driverinit_value_set(), and uses that as the default value
for a param.

Because default parameter values are optional, it would be impossible
to discern whether or not a param of type bool has default value of
false or not provided if the default value is encoded using a netlink
flag type. For this reason, when a DEVLINK_PARAM_TYPE_BOOL has an
associated default value, the default value is encoded using a u8
type.

Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20251119025038.651131-4-daniel.zahka@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Daniel Zahka
2025-11-18 18:50:33 -08:00
committed by Jakub Kicinski
parent 17a42aa465
commit 2a367002ed
6 changed files with 160 additions and 14 deletions
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10
Documentation/networking/devlink/devlink-params.rst
View File

@@ -41,6 +41,16 @@ In order for ``driverinit`` parameters to take effect, the driver must
support reloading via the ``devlink-reload`` command. This command will
request a reload of the device driver.
Default parameter values
=========================
Drivers may optionally export default values for parameters of cmode
``runtime`` and ``permanent``. For ``driverinit`` parameters, the last
value set by the driver will be used as the default value. Drivers can
also support resetting params with cmode ``runtime`` and ``permanent``
to their default values. Resetting ``driverinit`` params is supported
by devlink core without additional driver support needed.
.. _devlink_params_generic:
Generic configuration parameters