linux-kernel - Re: [PATCH net-next 06/16] net: pcs: xpcs: Avoid creating dummy XPCS MDIO device

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Date:   Tue, 5 Dec 2023 10:49:47 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Tomer Maimon <tmaimon77@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, openbmc@...ts.ozlabs.org,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 06/16] net: pcs: xpcs: Avoid creating dummy XPCS
 MDIO device

On Tue, Dec 05, 2023 at 01:35:27PM +0300, Serge Semin wrote:
> If the DW XPCS MDIO devices are either left unmasked for being auto-probed
> or explicitly registered in the MDIO subsystem by means of the
> mdiobus_register_board_info() method there is no point in creating the
> dummy MDIO device instance in order to get the DW XPCS handler since the
> MDIO core subsystem will create the device during the MDIO bus
> registration procedure.

Please reword this overly long sentence.

If they're left unmasked, what prevents them being created as PHY
devices?

> @@ -1437,19 +1435,21 @@ struct dw_xpcs *xpcs_create_mdiodev(struct mii_bus *bus, int addr,
>  	struct mdio_device *mdiodev;
>  	struct dw_xpcs *xpcs;
>  
> -	mdiodev = mdio_device_create(bus, addr);
> -	if (IS_ERR(mdiodev))
> -		return ERR_CAST(mdiodev);
> +	if (addr >= PHY_MAX_ADDR)
> +		return ERR_PTR(-EINVAL);
>  
> -	xpcs = xpcs_create(mdiodev, interface);
> +	if (mdiobus_is_registered_device(bus, addr)) {
> +		mdiodev = bus->mdio_map[addr];
> +		mdio_device_get(mdiodev);

No, this makes no sense now. This function is called
xpcs_create_mdiodev() - note the "create_mdiodev" part. If it's getting
the mdiodev from what is already there then it isn't creating it, so
it's no longer doing what it says in its function name. If you want to
add this functionality, create a new function to do it.

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