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Date: Fri, 2 Feb 2024 22:50:35 +0100
From: Andrew Lunn <andrew@lunn.ch>
To: Rob Herring <robh@kernel.org>
Cc: Christian Marangi <ansuelsmth@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	Frank Rowand <frowand.list@gmail.com>,
	Robert Marko <robert.marko@sartura.hr>, netdev@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org
Subject: Re: [net-next PATCH v5 6/9] dt-bindings: net: Document Qcom QCA807x
 PHY package
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 <20240201151747.7524-7-ansuelsmth@gmail.com>
 <20240202204536.GB1075521-robh@kernel.org>
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> > +patternProperties:
> > +  ^ethernet-phy(@[a-f0-9]+)?$:
> 
> I don't get how an address is optional.

Its pretty unusual, but for example:

arch/arm/boot/dts/nxp/imx/imx6q-novena.dts

&fec {
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_enet_novena>;
        phy-mode = "rgmii";
        phy-handle = <&ethphy>;
        phy-reset-gpios = <&gpio3 23 GPIO_ACTIVE_LOW>;
        status = "okay";

        mdio {
                #address-cells = <1>;
                #size-cells = <0>;

                ethphy: ethernet-phy {
                        compatible = "ethernet-phy-ieee802.3-c22";
                        rxc-skew-ps = <3000>;
                        rxdv-skew-ps = <0>;
                        txc-skew-ps = <3000>;
                        txen-skew-ps = <0>;
                        rxd0-skew-ps = <0>;
                        rxd1-skew-ps = <0>;
                        rxd2-skew-ps = <0>;
                        rxd3-skew-ps = <0>;
                        txd0-skew-ps = <3000>;
                        txd1-skew-ps = <3000>;
                        txd2-skew-ps = <3000>;
                        txd3-skew-ps = <3000>;
                };
        };
};

There is no reg property, because its optional. If there is no reg,
there is no address.

When phylib finds a DT blob like this, it enumerates the bus, and then
assigns the nodes to the devices it finds in the order it finds them.

Its old behaviour, from before the times of yaml validation, and
current best practices, etc. But because it works, it still used in
new bindings.

    Andrew