linux-kernel - Re: [PATCH v13 1/3] dt-bindings: i2c: Add CP2112 HID USB to SMBus Bridge

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Message-ID: <aXoz4Xs8csdxXeZU@smile.fi.intel.com>
Date: Wed, 28 Jan 2026 18:05:53 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Danny Kaehn <danny.kaehn@...xus.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Benjamin Tissoires <bentiss@...nel.org>,
	Andi Shyti <andi.shyti@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	devicetree@...r.kernel.org, linux-input@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Ethan Twardy <ethan.twardy@...xus.com>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, Leo Huang <leohu@...dia.com>,
	Arun D Patil <arundp@...dia.com>, Willie Thai <wthai@...dia.com>,
	Ting-Kai Chen <tingkaic@...dia.com>
Subject: Re: [PATCH v13 1/3] dt-bindings: i2c: Add CP2112 HID USB to SMBus
 Bridge

On Wed, Jan 28, 2026 at 04:48:18PM +0100, Krzysztof Kozlowski wrote:
> On 28/01/2026 13:49, Andy Shevchenko wrote:
> > On Wed, Jan 28, 2026 at 11:35:25AM +0100, Krzysztof Kozlowski wrote:
> >> On Tue, Jan 27, 2026 at 10:02:17AM -0600, Danny Kaehn wrote:

...

> >> That's actually rule communicated many times, also documented in writing
> >> bindings and in recent talks.
> > 
> > Does DT represents HW in this case? Shouldn't I²C controller be the same node?
> > Why not? This is inconsistent for the device that is multi-functional. And from
> > my understanding the firmware description (DT, ACPI, you-name-it) must follow
> > the HW. I don't see how it's done in this case.
> 
> What is inconsistent exactly? What sort of rule tells that every little
> function needs a device node? It's first time I hear about any of such
> rule and for all this time we already NAKed it so many times (node per
> GPIO, node per clock, node per every little pin).

That we should represent the HW as is. There is no "rule", there is a common
sense. Of course, it's possible to have all-in-one node, but this may lead
to a disaster when there are tons of devices in the Multi Functional HW
and some of them use the same properties. How would you distinguish HW
with two GPIO banks, two I²C controllers, et cetera? That's what my common
sense tells to me, putting all eggs into one bucket is just a mine field
for the future.

-- 
With Best Regards,
Andy Shevchenko