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
older userapace binaries.

The fourth patch introduces the 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

CHANGES:
v4:
  - add test case for default params.
  - add new cmode runtime test param to netdevsim.
  - introduce uapi and driver api for supporting default param values.
  - rename device_default to default in mlx5 patch.
v3: https://lore.kernel.org/netdev/20251107204347.4060542-1-daniel.zahka@gmail.com/ (local)
  - fix warnings about undocumented param in intel ice driver
v2: https://lore.kernel.org/netdev/20251103194554.3203178-1-daniel.zahka@gmail.com/ (local)
  - fix indentation issue in new mlx5.rst entry
  - use extack in mlx5_nv_param_devlink_swp_l4_csum_mode_get()
  - introduce extack patch.
v1: https://lore.kernel.org/netdev/20251022190932.1073898-1-daniel.zahka@gmail.com/ (local)

Daniel Zahka (6):
  devlink: pass extack through to devlink_param::get()
  devlink: refactor devlink_nl_param_value_fill_one()
  devlink: support default values for param-get and param-set
  net/mlx5: implement swp_l4_csum_mode via devlink params
  netdevsim: register a new devlink param with default value interface
  selftest: netdevsim: test devlink default params

 Documentation/netlink/specs/devlink.yaml      |   9 +
 .../networking/devlink/devlink-params.rst     |  10 +
 Documentation/networking/devlink/mlx5.rst     |  14 ++
 .../marvell/octeontx2/otx2_cpt_devlink.c      |   6 +-
 drivers/net/ethernet/amd/pds_core/core.h      |   3 +-
 drivers/net/ethernet/amd/pds_core/devlink.c   |   3 +-
 .../net/ethernet/broadcom/bnxt/bnxt_devlink.c |   6 +-
 .../net/ethernet/intel/i40e/i40e_devlink.c    |   3 +-
 .../net/ethernet/intel/ice/devlink/devlink.c  |  14 +-
 .../marvell/octeontx2/af/rvu_devlink.c        |  15 +-
 .../marvell/octeontx2/nic/otx2_devlink.c      |   6 +-
 drivers/net/ethernet/mellanox/mlx4/main.c     |   6 +-
 .../net/ethernet/mellanox/mlx5/core/devlink.h |   3 +-
 .../net/ethernet/mellanox/mlx5/core/eswitch.c |   3 +-
 .../mellanox/mlx5/core/eswitch_offloads.c     |   3 +-
 .../net/ethernet/mellanox/mlx5/core/fs_core.c |   3 +-
 .../ethernet/mellanox/mlx5/core/fw_reset.c    |   3 +-
 .../mellanox/mlx5/core/lib/nv_param.c         | 238 +++++++++++++++++-
 .../mellanox/mlxsw/spectrum_acl_tcam.c        |   3 +-
 .../ethernet/netronome/nfp/devlink_param.c    |   3 +-
 drivers/net/ethernet/qlogic/qed/qed_devlink.c |   3 +-
 .../net/ethernet/stmicro/stmmac/stmmac_main.c |   3 +-
 drivers/net/ethernet/ti/am65-cpsw-nuss.c      |   3 +-
 drivers/net/ethernet/ti/cpsw_new.c            |   6 +-
 drivers/net/netdevsim/dev.c                   |  55 ++++
 drivers/net/netdevsim/netdevsim.h             |   1 +
 drivers/net/wwan/iosm/iosm_ipc_devlink.c      |   3 +-
 include/net/devlink.h                         |  45 +++-
 include/net/dsa.h                             |   3 +-
 include/uapi/linux/devlink.h                  |   3 +
 net/devlink/netlink_gen.c                     |   5 +-
 net/devlink/param.c                           | 180 +++++++++----
 net/dsa/devlink.c                             |   3 +-
 .../drivers/net/netdevsim/devlink.sh          | 113 ++++++++-
 34 files changed, 689 insertions(+), 91 deletions(-)

-- 
2.47.3