linux-kernel - Re: [PATCH net-next v2] net: stmmac: don't create a MDIO bus if unnecessary

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Message-ID: <9eddb32d-c798-4e1b-b0ea-c44d31cc29bf@lunn.ch>
Date:   Fri, 8 Dec 2023 14:14:41 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Andrew Halaney <ahalaney@...hat.com>
Cc:     Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Serge Semin <fancer.lancer@...il.com>
Subject: Re: [PATCH net-next v2] net: stmmac: don't create a MDIO bus if
 unnecessary

> I know you said the standard is to make the MDIO bus unconditionally, but
> to me that feels like a waste, and describing say an empty MDIO bus
> (which would set the phy_mask for us eventually and not scan a
> bunch of phys, untested but I think that would work) seems like a bad
> description in the devicetree (I could definitely see describing an
> empty MDIO bus getting NACKed, but that's a guess).

DT describes the hardware. The MDIO bus master exists. So typically
the SoC .dtsi file would include it in the Ethernet node. At the SoC
level it is empty, unless there is an integrated PHY in the SoC. The
board .dts file then adds any PHYs to the node which the board
actually has.

So i doubt adding an empty MDIO node to the SoC .dtsi file will get
NACKed, it correctly describes the hardware.

	Andrew