Re: [RFC net-next v2 2/6] ethtool: Add loopback GET/SET netlink implementation

["Björn Töpel" <bjorn@kernel.org>]

Maxime Chevallier <maxime.chevallier@bootlin.com> writes:

> Hi Björn,
>
> On 08/03/2026 13:40, Björn Töpel wrote:
>> Add the kernel-side ETHTOOL_MSG_LOOPBACK_GET,
>> ETHTOOL_MSG_LOOPBACK_SET, and ETHTOOL_MSG_LOOPBACK_NTF handlers using
>> the standard ethnl_request_ops infrastructure.
>> 
>> GET collects loopback entries from per-component helpers via
>> loopback_get_entries(). SET parses the nested entry attributes,
>> dispatches each to loopback_set_one(), and only sends a notification
>> when the state is changed.
>> 
>> No components are wired yet.
>> 
>> Signed-off-by: Björn Töpel <bjorn@kernel.org>
>
> At a first glance, what I see is that you're using the GET ->doit method
> to retrieve an array of loopback entries. The pefered approach in that
> case is to use the GET ->dumpit command instead, issueing a netlink DUMP
> request to list all available loopback entities on a given netdev.
>
> If you want some reference on that, take a look at the phy.c + the
> 'perphy' helpers in net/ethtool/netlink.c
>
> The idea is that you can pass a netdev ifindex in the header of the DUMP
> request, which you can use to dump all loopbacks the passed netdev.
>
> You can also check the ethtool code itself, you'll see that when you use
> the "ethtool --show-phys eth0" command for example, it issues a DUMP
> request to the kernel.

Ah, got it! Thanks!

> I'll continue the review w.r.t the actual content of the messages :)

...and thank you!


Björn