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

Maxime Chevallier
2025-03-24T10:40:23Z

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(-)

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2.48.1