linux-kernel - Re: [PATCH v2 1/3] dt-bindings: usb: usb251xb: make reg optional for no I2C ctrl use case

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Message-ID: <aKRgfFpF8thM3vjr@xhacker>
Date: Tue, 19 Aug 2025 19:31:08 +0800
From: Jisheng Zhang <jszhang@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Richard Leitner <richard.leitner@...ux.dev>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-usb@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: usb: usb251xb: make reg optional for
 no I2C ctrl use case

On Tue, Aug 19, 2025 at 11:22:51AM +0200, Krzysztof Kozlowski wrote:
> On Tue, Aug 19, 2025 at 08:22:15AM +0800, Jisheng Zhang wrote:
> > Make "reg" optional to allow the driver to be used to manage GPIO
> > based control of the device.
> 
> I don't understand how optional reg allows or disallows anything for the
> driver. It's really not relevant to GPIO at all.

w/o this patch, then there will be DT check complains for the following
usb251xb usage:

usb-hub {
	compatible = "microchip,usb2512b";
	reset-gpios = <&porta 2 GPIO_ACTIVE_LOW>;
};


> 
> Also feels wrong, but maybe you just lack proper, reasonable
> justification. Just explain carefully the hardware, not drivers.

It's simple, the hub allows usage w/o connecting to any i2c, see above
example for reference. But current dt-binding make the reg required.

Regards.