Re: [PATCH net-next v5 07/13] net: ethtool: Introduce a command to list PHYs on an interface

On Wed, 24 Jan 2024 17:54:53 +0100
Andrew Lunn [off-list ref] wrote:

quoted

quoted

Another option might be to add PHY support to netdevsim. Add a debugfs
interface to allow you to create arbitrary PHY topologies? You can
then even add a test script.  

Sorry for the delayed answer, I just took a few hours to give it a try,
and I was able to spin some very basic PHY support for the netdevsim,
allowing to attach arbitrary instances of fixed_phy devices. I can
therefore use that as a mean of testing the dump operation, I'll try to
include that in the next iteration, that should pave the way for some
testability of more PHY stuff hopefully.  

Great that you looked at this.

FYI: Jakub would like to see changes to netdevsim accompanied with
self tests making you of the features you add. There is also now a
build bot running the self tests against net-next, so these tests
should get run quite frequently.

No problem, I'll include these as well.

I do face a problem with fixed_phy though now that I've played around
with it. As fixed_phys share the same global MDIO bus, what can happen
is that netdevsim-registered PHYs can starve the dummy MDIO bus by
exhausting all 32 mdio addresses, preventing real interfaces from
getting their own fixed-phy instance.

I'll probably register a dedicated mdio bus per netdevsim (or even
per-phy, so that we can imagine controling the returned register
values), let's see how it goes.

Thanks,

Maxime