linux-kernel - Re: [PATCH v3 1/2] modpost: file2alias: make mdio alias configure match mdio uevent

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Date:   Sun, 5 Dec 2021 19:02:48 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Yinbo Zhu <zhuyinbo@...ngson.cn>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v3 1/2] modpost: file2alias: make mdio alias configure
 match mdio uevent

On Sun, Dec 05, 2021 at 04:56:44PM +0100, Andrew Lunn wrote:
> > This patch changes the MODALIAS entry for only PHY devices from:
> > 	MODALIAS=of:Nethernet-phyT(null)
> > to:
> > 	MODALIAS=mdio:00000000001000100001010100010011
> 
> Hi Russell
> 
> You patch looks good for the straight forward cases.
> 
> What happens in the case of
> 
>         ethernet-phy@0 {
>             compatible = "ethernet-phy-ieee802.3-c45";
> 
> 
> Does this get appended to the end, or does it overwrite?

Hmm, good point, I'd forgotten about clause 45 PHYs - we need to dig
the first existing ID out of the clause 45 ID array and use that
instead. That said, we don't publish the ID through the "phy_id"
sysfs file either for clause 45.

I don't believe it's possible to publish multiple modalias strings.

This gives a problem for clause 45 PHYs which can have a different ID
for each MMD, and the driver might match on only one of those. 88x3310
is an example where different MMDs have different IDs. The mechanism
we have in phy_device_create() gets around that, because we call
phy_request_driver_module() for every ID there is in the hope that one
of those will load the appropriate driver, but as I say, I don't
believe that's a possibility via the udev approach.

So I think we may have to say that clause 45 PHYs can't reliably use
the conventional udev mechanism.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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