linux-kernel - Re: [PATCH net-next 07/15] mfd: core: add ability for cells to probe on a custom parent OF node

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Message-ID: <20251120153622.p6sy77coa3de6srw@skbuf>
Date: Thu, 20 Nov 2025 17:36:22 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: Lee Jones <lee@...nel.org>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 07/15] mfd: core: add ability for cells to probe
 on a custom parent OF node

On Thu, Nov 20, 2025 at 02:41:36PM +0000, Lee Jones wrote:
> On Tue, 18 Nov 2025, Vladimir Oltean wrote:
> 
> > I would like the "nxp,sja1110a" driver, in the configuration below, to
> > be able to probe the drivers for "nxp,sja1110-base-t1-mdio" and for
> > "nxp,sja1110-base-tx-mdio" via mfd_add_devices():
> > 
> > 	ethernet-switch@0 {
> > 		compatible = "nxp,sja1110a";
> > 
> > 		mdios {
> > 			mdio@0 {
> > 				compatible = "nxp,sja1110-base-t1-mdio";
> > 			};
> > 
> > 			mdio@1 {
> > 				compatible = "nxp,sja1110-base-tx-mdio";
> > 			};
> > 		};
> > 	};
> 
> This device is not an MFD.
> 
> Please find a different way to instantiate these network drivers.

Ok.. but what is an MFD? I'm seriously interested in a definition.

One data point: the VSC7512 (driver in drivers/mfd/ocelot-spi.c,
bindings in Documentation/devicetree/bindings/mfd/mscc,ocelot.yaml) is
almost the same class of hardware (except the embedded Cortex-M7 in
SJA1110 can't run Linux, and the CPU in VSC7512 can). It instantiates
MDIO bus children, like this patch proposes too, except it works with a
different device tree hierarchy which I need to adapt to, without breaking.