[PATCH v4 net 0/8] Fix short frame transmission in enetc

[vladimir . oltean]

This is a belated follow-up to Zefir Kurtisi's report:
https://lore.kernel.org/netdev/20260220132930.2521155-1-zefir.kurtisi@xxxxxxxxx/

which is that the ENETC misbehaves when transmitting packets smaller
than 16 octets sans FCS: it sends them but does not update the completed
index in the transmit BD ring. I did find a sentence in the reference
manual explicitly stating these short frames are not supported.

The original series was focused on handling the invalid frame
geometries (now patches 4, 5 and 6). However, review pointed out further
issues in annex code. The other patches handle those.

v1 at:
https://lore.kernel.org/netdev/20260401172246.1075883-1-vladimir.oltean@xxxxxxx/

v2 at:
https://lore.kernel.org/netdev/20260406204122.167237-1-vladimir.oltean@xxxxxxx/

v3 at:
https://lore.kernel.org/netdev/20260915222735.1016937-5-vladimir.oltean@xxxxxxx/

Change log in individual patches. At a high level:
- applied feedback from Wei Fang, David Laight and Sashiko
- dropped "[PATCH v3 net 7/7] net: enetc: drain and cancel one-step TX
  tstamp queue when going down" because addressing Sashiko's feedback
  would grow this series to a point where it would become impossible to
  make any progress; plus it becomes more and more unrelated to the main
  objective. Will address that part separately.
- dropped "[PATCH v3 net 6/7] net: enetc: linearize PTP event packets
  with one-step TX timestamping"; also unrelated to short frames, will
  resubmit separately.
- split v3's "pad short frames in software" into patch 4 (do not rely on
  mEMAC hardware frame padding) and patch 5 (ensure head buffer has at
  least 16 octets).
- reworked v3's "pad short XDP frames coming from devmap": instead of
  padding the xdp_frame in place through a new generic xdp_frame_pad()
  helper (which only covered ndo_xdp_xmit()), patch 6 now pads in the
  driver using the shared tx_pad buffer, covering the XDP_TX path too.
  Consequently, there is no longer a change to include/net/xdp.h, so the
  BPF/XDP folks are no longer CCed.
- new patches:
  - 2/8: serialize access to the same TX ring from NAPI XDP_TX and
    ndo_xdp_xmit()
  - 7/8: fix leak of pending XDP_TX frames when going down

Vladimir Oltean (8):
  net: enetc: consistently track dropped frames in enetc_xdp_xmit()
  net: enetc: serialize access to the same TX ring from NAPI XDP_TX and
    ndo_xdp_xmit()
  net: enetc: fix bogus TX ring consumer index after reinitialization
  net: enetc: do not rely on mEMAC hardware frame padding
  net: enetc: ensure head buffer has at least 16 octets
  net: enetc: pad short XDP frames in software
  net: enetc: fix leak of pending XDP_TX frames when going down
  net: enetc: ensure enetc_xdp_xmit() calls enetc_update_tx_ring_tail()

 drivers/net/ethernet/freescale/enetc/enetc.c | 160 ++++++++++++++++---
 drivers/net/ethernet/freescale/enetc/enetc.h |  12 ++
 2 files changed, 148 insertions(+), 24 deletions(-)

-- 
2.43.0