[PATCH iwl-next v5 0/3] igb: add RSS key get/set support

[Takashi Kozu <takkozu@amazon.com>]

This series adds ethtool get/set support for the RSS hash key in the igb
driver.
- `ethtool -x <dev>` to display the RSS key
- `ethtool -X <dev> hkey <key>` to configure the RSS key

Without patch:

# ethtool -x $DEV | grep key -A1
RSS hash key:
Operation not supported
# ethtool -X $DEV hkey 00:00:00:00:00:00:00:00:00:00:00:00:000
Cannot set RX flow hash configuration:
  Hash key setting not supported


With patch:

# ethtool -x $DEV | grep key -A1
RSS hash key:
86:5d:11:56:bd:6f:20:38:3b:f8:bb:df:00:3a:b0:24:95:9f:f9:f4:25:a3:01:3e:4a:15:d6:7c:4d:af:39:7e:4a:95:f2:fd:f6:b6:26:f7

# ethtool -X $DEV hkey 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00
# ethtool -x $DEV | grep key -A1
RSS hash key:
00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00

<Changelog>
  v5:
      - delete 'has_user_rss_key' flag because it's unnecessary. 

  v4: 
      - modify the position of the declaration in the igb_write_rss_key() so that it is at the start of the block.

  v3: 
      - add ASSERT_RTNL() to explicitly show that an rtnl lock is being used
      - Move netdev_rss_key_fill() function from igb_setup_mrqc() to igb_sw_init()
      - Add kernel-doc header to igb_write_rss_key()

      <Test>
      - tools/testing/selftests/drivers/net/hw/rss_api.py is successful
      Run the following command

      # NETIF=enp0s3 python tools/testing/selftests/drivers/net/hw/rss_api.py | grep -v "# Exception" 

      Then, I checked the diffs before and after applying the patch

      $ diff beforePatch.txt afterPatch.txt 
      9c9
      < not ok 6 rss_api.test_rxfh_nl_set_key
      ---
      > ok 6 rss_api.test_rxfh_nl_set_key
      16c16
      < # Totals: pass:4 fail:8 xfail:0 xpass:0 skip:0 error:0
      ---
      > # Totals: pass:5 fail:7 xfail:0 xpass:0 skip:0 error:0

      The failing tests originally fails due to hardware.

      - tools/testing/selftests/drivers/net/hw/toeplitz.py is untested since there is no actual hardware, but since the logic around wr32() is preserved as it is, key writing to the device remain the same.
      

  v2: Fix typos (igc_* → igb_*) 
      https://lore.kernel.org/intel-wired-lan/20260108052020.84218-5-takkozu@amazon.com/T/

  v1: https://lore.kernel.org/all/20251205082106.4028-5-takkozu@amazon.com/

Takashi Kozu (3):
  igb: prepare for RSS key get/set support
  igb: expose RSS key via ethtool get_rxfh
  igb: allow configuring RSS key via ethtool set_rxfh

 drivers/net/ethernet/intel/igb/igb.h         |  3 +
 drivers/net/ethernet/intel/igb/igb_ethtool.c | 85 ++++++++++++++------
 drivers/net/ethernet/intel/igb/igb_main.c    |  8 +-
 3 files changed, 66 insertions(+), 30 deletions(-)

-- 
2.52.0