linux-kernel - Re: [PATCH 2/2] net: mdio: support c45 peripherals on c22 busses

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Message-ID: <YGuPcNPXiQZkEehh@arch-linux>
Date:   Tue, 6 Apr 2021 00:30:08 +0200
From:   Danilo Krummrich <danilokrummrich@...develop.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        davem@...emloft.net, hkallweit1@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, jeremy.linton@....com
Subject: Re: [PATCH 2/2] net: mdio: support c45 peripherals on c22 busses

On Mon, Apr 05, 2021 at 09:27:44PM +0200, Andrew Lunn wrote:
> > Now, instead of encoding this information of the bus' capabilities at both
> > places, I'd propose just checking the mii_bus->capabilities field in the
> > mdiobus_c45_*() functions. IMHO this would be a little cleaner, than having two
> > places where this information is stored. What do you think about that?
> 
> You will need to review all the MDIO bus drivers to make sure they
> correctly set the capabilities. There is something like 55 using
> of_mdiobus_register() and 45 using mdiobus_register(). So you have 100
> drivers to review.
Yes, but I think it would be enough to look at the drivers handling the
MII_ADDR_C45 flag, because those are either
- actually capable to do C45 bus transfers or
- do properly return -EOPNOTSUPP.

I counted 27 drivers handling the MII_ADDR_C45 flag. Setting the capabilities
for those should be pretty easy.

The remaining ones, which should be about 73 then, could be left untouched,
because the default capability MDIOBUS_NO_CAP would indicate they can C22 only.
Since they don't handle the MII_ADDR_C45 flag at all, this should be the
correct assumption.
> 
> 	Andrew
>