[PATCH net-next v4 0/8] net: ethtool: Introduce ethnl dump helpers

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi everyone,

This is V4 for the ethnl dump support, allowing better handling of
per-phy dump but also any other dump operation that needs to dump more
than one message per netdev.

Changes in V4:
 - Don't grab rcu_read_lock when we already have a refcounter netdev on
   the filtered dump path (Paolo)
 - Move the dump_all stuff in a dedicated helper (Paolo)
 - Added patch 1 to set the dev in ctx->req_info

Changes in V3:
 - Fixed some typos and xmas tree issues
 - Added a missing check for EOPNOTSUPP in patch 1
 - Added missing kdoc
 - Added missing comments in phy_reply_size

Changes in V2:
 - Rebased on the netdev_lock work by Stanislav and the fixes from Eric
 - Fixed a bissectability issue
 - Fixed kdoc for the new ethnl ops and fields

V1: https://lore.kernel.org/netdev/20250305141938.319282-1-maxime.chevallier@bootlin.com/
V2: https://lore.kernel.org/netdev/20250308155440.267782-1-maxime.chevallier@bootlin.com/
V3: https://lore.kernel.org/netdev/20250313182647.250007-1-maxime.chevallier@bootlin.com/

As of today when using ethnl's default ops, the DUMP requests will
simply perform a GET for each netdev.

That hits limitations for commands that may return multiple messages for
a single netdev, such as :

 - RSS (listing contexts)
 - All PHY-specific commands (PLCA, PSE-PD, phy)
 - tsinfo (one item for the netdev +  one per phy)

 Commands that need a non-default DUMP support have to re-implement
 ->dumpit() themselves, which prevents using most of ethnl's internal
 circuitry.

This series therefore introduces a better support for dump operations in
ethnl.

The patches 1 and 2 introduce the support for filtered DUMPs, where an
ifindex/ifname can be passed in the request header for the DUMP
operation. This is for when we want to dump everything a netdev
supports, but without doing so for every single netdev. ethtool's
"--show-phys ethX" option for example performs a filtered dump.

Patch 3 introduces 3 new ethnl ops : 
 ->dump_start() to initialize a dump context
 ->dump_one_dev(), that can be implemented per-command to dump
 everything on a given netdev
 ->dump_done() to release the context

The default behaviour for dumps remains the same, calling the whole
->doit() path for each netdev.

Patch 4 introduces a set of ->dump_start(), ->dump_one_dev() and
->dump_done() callback implementations that can simply be plugged into
the existing commands that list objects per-phy, making the 
phy-targeting command behaviour more coherent.

Patch 5 uses that new set of helpers to rewrite the phy.c support, which
now uses the regulat ethnl_ops instead of fully custom genl ops. This
one is the hardest to review, sorry about that, I couldn't really manage
to incrementally rework that file :(

Patches 6 and 7 are where the new dump infra shines, adding per-netdev
per-phy dump support for PLCA and PSE-PD.

We could also consider converting tsinfo/tsconfig, rss and tunnels to
these new ->dump_***() operations as well, but that's out of this
series' scope.

Thanks,

Maxime



Maxime Chevallier (8):
  net: ethtool: Set the req_info->dev on DUMP requests for each dev
  net: ethtool: netlink: Allow per-netdevice DUMP operations
  net: ethtool: netlink: Rename ethnl_default_dump_one
  net: ethtool: netlink: Introduce command-specific dump_one_dev
  net: ethtool: netlink: Introduce per-phy DUMP helpers
  net: ethtool: phy: Convert the PHY_GET command to generic phy dump
  net: ethtool: plca: Use per-PHY DUMP operations
  net: ethtool: pse-pd: Use per-PHY DUMP operations

 net/ethtool/netlink.c | 185 ++++++++++++++++++-----
 net/ethtool/netlink.h |  47 +++++-
 net/ethtool/phy.c     | 344 ++++++++++++------------------------------
 net/ethtool/plca.c    |  12 ++
 net/ethtool/pse-pd.c  |   6 +
 5 files changed, 310 insertions(+), 284 deletions(-)

-- 
2.48.1