Re: [PATCH net-next 0/7] net: ethtool: Introduce ethnl dump helpers

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

On Wed,  5 Mar 2025 15:19:30 +0100
Maxime Chevallier <maxime.chevallier@bootlin.com> wrote:

> Hi everyone,
> 
> This series adds some scaffolding into ethnl to ease the support of
> DUMP operations.
> 
> 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.
> 
> I've tested that series with some netdevsim PHY patches that I plan to
> submit (they can be found here [1]), with the refcount tracker
> for net/netns enabled to make sure the lock usage is somewhat coherent.
> 
> Thanks,
> 
> Maxime
> 
> [1]: https://github.com/minimaxwell/linux/tree/mc/netdevsim-phy
> 

This series will very likely conflict with Stanislav's netdev lock
work [2], I'll of course be happy to rebase should it get merged :)

Thanks,

Maxime

[2]: https://lore.kernel.org/netdev/20250305163732.2766420-1-sdf@fomichev.me/T/#t

> 
> Maxime Chevallier (7):
>   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 | 161 ++++++++++++++------
>  net/ethtool/netlink.h |  46 +++++-
>  net/ethtool/phy.c     | 335 ++++++++++++------------------------------
>  net/ethtool/plca.c    |  12 ++
>  net/ethtool/pse-pd.c  |   6 +
>  5 files changed, 277 insertions(+), 283 deletions(-)
>