Merge branch 'Traffic-support-for-SJA1105-DSA-driver'

Vladimir Oltean says:

====================
Traffic support for SJA1105 DSA driver

This patch set is a continuation of the "NXP SJA1105 DSA driver" v3
series, which was split in multiple pieces for easier review.

Supporting a fully-featured (traffic-capable) driver for this switch
requires some rework in DSA and also leaves behind a more generic
infrastructure for other dumb switches that rely on 802.1Q pseudo-switch
tagging for port separation. Among the DSA changes required are:

* Generic xmit and rcv functions for pushing/popping 802.1Q tags on
  skb's. These are modeled as a tagging protocol of its own but which
  must be customized by drivers to fit their own hardware possibilities.

* Permitting the .setup callback to invoke switchdev operations that
  will loop back into the driver through the switchdev notifier chain.

The SJA1105 driver then proceeds to extend this 8021q switch tagging
protocol while adding its own (tag_sja1105). This is done because
the driver actually implements a "dual tagger":

* For normal traffic it uses 802.1Q tags

* For management (multicast DMAC) frames the switch has native support
  for recognizing and annotating these with source port and switch id
  information.

Because this is a "dual tagger", decoding of management frames should
still function when regular traffic can't (under a bridge with VLAN
filtering).
There was intervention in the DSA receive hotpath, where a new
filtering function called from eth_type_trans() is needed. This is
useful in the general sense for switches that might actually have some
limited means of source port decoding, such as only for management
traffic, but not for everything.
In order for the 802.1Q tagging protocol (which cannot be enabled under
all conditions, unlike the management traffic decoding) to not be an
all-or-nothing choice, the filtering function matches everything that
can be decoded, and everything else is left to pass to the master
netdevice.

Lastly, DSA core support was added for drivers to request skb deferral.
SJA1105 needs this for SPI intervention during transmission of link-local
traffic. This is not done from within the tagger.

Some patches were carried over unchanged from the previous patchset
(01/09). Others were slightly reworked while adapting to the recent
changes in "Make DSA tag drivers kernel modules" (02/09).

The introduction of some structures (DSA_SKB_CB, dp->priv) may seem a
little premature at this point and the new structures under-utilized.
The reason is that traffic support has been rewritten with PTP
timestamping in mind, and then I removed the timestamping code from the
current submission (1. it is a different topic, 2. it does not work very
well yet). On demand I can provide the timestamping patchset as a RFC
though.

"NXP SJA1105 DSA driver" v3 patchset can be found at:
https://lkml.org/lkml/2019/4/12/978

v1 patchset can be found at:
https://lkml.org/lkml/2019/5/3/877

Changes in v2:

* Made the deferred xmit workqueue also be drained on the netdev suspend
  callback, not just on ndo_stop.

* Added clarification about how other netdevices may be bridged with the
  switch ports.

v2 patchset can be found at:
https://www.spinics.net/lists/netdev/msg568818.html

Changes in v3:

* Exported the dsa_port_vid_add and dsa_port_vid_del symbols to fix an
  error reported by the kbuild test robot

* Fixed the following checkpatch warnings in 05/10:
  Macro argument reuse 'skb' - possible side-effects?
  Macro argument reuse 'clone' - possible side-effects?

* Added a commit description to the documentation patch (10/10)
====================

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