Merge branch 'devlink-net-mlx5-implement-swp_l4_csum_mode-via-devlink-params'

Daniel Zahka says:

====================
devlink: net/mlx5: implement swp_l4_csum_mode via devlink params

This series introduces a new devlink feature for querying param
default values, and resetting params to their default values. This
feature is then used to implement a new mlx5 driver param.

The series starts with two pure refactor patches: one that passes
through the extack to devlink_param::get() implementations. And a
second small refactor that prepares the netlink tlv handling code in
the devlink_param::get() path to better handle default parameter
values.

The third patch introduces the uapi and driver api for default
parameter values. The driver api is opt-in, and both the uapi and
driver api preserve existing behavior when not used by drivers or
userspace.

The fourth patch introduces a new mlx5 driver param, swp_l4_csum_mode,
for controlling tx csum behavior. The "l4_only" value of this param is
a dependency for PSP initialization on CX7 NICs.

Lastly, the series introduces a new driver param with cmode runtime to
netdevsim, and then uses this param in a new testcase for netdevsim
devlink params.

Here are some examples of using the default param uapi with the devlink
cli. Note the devlink cli binary I am using has changes which I am
posting in accompanying series targeting iproute2-next:

# netdevsim
./devlink dev param show netdevsim/netdevsim0
netdevsim/netdevsim0:
name max_macs type generic
values:
cmode driverinit value 32 default 32
name test1 type driver-specific
values:
cmode driverinit value true default true

# set to false
./devlink dev param set netdevsim/netdevsim0 name test1 value false cmode driverinit
./devlink dev param show netdevsim/netdevsim0
netdevsim/netdevsim0:
name max_macs type generic
values:
cmode driverinit value 32 default 32
name test1 type driver-specific
values:
cmode driverinit value false default true

# set back to default
./devlink dev param set netdevsim/netdevsim0 name test1 default cmode driverinit
./devlink dev param show netdevsim/netdevsim0
netdevsim/netdevsim0:
name max_macs type generic
values:
cmode driverinit value 32 default 32
name test1 type driver-specific
values:
cmode driverinit value true default true

# mlx5 params on cx7
./devlink dev param show pci/0000:01:00.0
pci/0000:01:00.0:
name max_macs type generic
values:
cmode driverinit value 128 default 128
...
name swp_l4_csum_mode type driver-specific
values:
cmode permanent value default default default

# set to l4_only
./devlink dev param set pci/0000:01:00.0 name swp_l4_csum_mode value l4_only cmode permanent
./devlink dev param show pci/0000:01:00.0 name swp_l4_csum_mode
pci/0000:01:00.0:
name swp_l4_csum_mode type driver-specific
values:
cmode permanent value l4_only default default

# reset to default
./devlink dev param set pci/0000:01:00.0 name swp_l4_csum_mode default cmode permanent
./devlink dev param show pci/0000:01:00.0 name swp_l4_csum_mode
pci/0000:01:00.0:
name swp_l4_csum_mode type driver-specific
values:
cmode permanent value default default default
====================

Link: https://patch.msgid.link/20251119025038.651131-1-daniel.zahka@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>