Merge branch 'Traffic-support-for-dsa_8021q-in-vlan_filtering-1-mode'

Vladimir Oltean says:

====================
Traffic support for dsa_8021q in vlan_filtering=1 mode

This series is an attempt to support as much as possible in terms of
traffic I/O from the network stack with the only dsa_8021q user thus
far, sja1105.

The hardware doesn't support pushing a second VLAN tag to packets that
are already tagged, so our only option is to combine the dsa_8021q with
the user tag into a single tag and decode that on the CPU.

The assumption is that there is a type of use cases for which 7 VLANs
per port are more than sufficient, and that there's another type of use
cases where the full 4096 entries are barely enough. Those use cases are
very different from one another, so I prefer trying to give both the
best experience by creating this best_effort_vlan_filtering knob to
select the mode in which they want to operate in.

v2 was submitted here:
https://patchwork.ozlabs.org/project/netdev/cover/20200511135338.20263-1-olteanv@gmail.com/

v1 was submitted here:
https://patchwork.ozlabs.org/project/netdev/cover/20200510164255.19322-1-olteanv@gmail.com/

Changes in v3:
Patch 01/15:
- Rename again to configure_vlan_while_not_filtering, and add a helper
  function for skipping VLAN configuration.
Patch 03/15:
- Remove sja1105_can_use_vlan_as_tags from driver code.
Patch 06/15:
- Adapt sja1105 driver to the second variable name change.
Patch 08/15:
- Provide an implementation of sja1105_can_use_vlan_as_tags as part of
  the tagger and not as part of the switch driver. So we have to look at
  the skb only, and not at the VLAN awareness state.

Changes in v2:
Patch 01/15:
- Rename variable from vlan_bridge_vtu to configure_vlans_while_disabled.
Patch 03/15:
- Be much more thorough, and make sure that things like virtual links
  and FDB operations still work properly.
Patch 05/15:
- Free the vlan lists on teardown.
- Simplify sja1105_classify_vlan: only look at priv->expect_dsa_8021q.
- Keep vid 1 in the list of dsa_8021q VLANs, to make sure that untagged
  packets transmitted from the stack, like PTP, continue to work in
  VLAN-unaware mode.
Patch 06/15:
- Adapt to vlan_bridge_vtu variable name change.
Patch 11/15:
- In sja1105_best_effort_vlan_filtering_set, get the vlan_filtering
  value of each port instead of just one time for port 0. Normally this
  shouldn't matter, but it avoids issues when port 0 is disabled in
  device tree.
Patch 14/14:
- Only do anything in sja1105_build_subvlans and in
  sja1105_build_crosschip_subvlans when operating in
  SJA1105_VLAN_BEST_EFFORT state. This avoids installing VLAN retagging
  rules in unaware mode, which would cost us a penalty in terms of
  usable frame memory.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>