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

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Message-ID: <aXknU-fxh286Nkek@smile.fi.intel.com>
Date: Tue, 27 Jan 2026 23:00:03 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Danny Kaehn <danny.kaehn@...xus.com>
Cc: 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 Tue, Jan 27, 2026 at 10:02:17AM -0600, Danny Kaehn wrote:
> On Tue, Jan 27, 2026 at 08:47:48AM -0600, Danny Kaehn wrote:
> > This is a USB HID device which includes an I2C controller and 8 GPIO pins.
> > 
> > The binding allows describing the chip's gpio and i2c controller in DT,
> > with the i2c controller being bound to a subnode named "i2c". This is
> > intended to be used in configurations where the CP2112 is permanently
> > connected in hardware.

> Hi Folks (Intended for Rob or Krzysztof),
> 
> Wasn't sure the best way to go about this, but trying to see the best
> way to get a message in front of you regarding an ask from Andy S.
> 
> In [1], Rob H initially directed that the gpio chip share a node with
> the CP2112 itself, rather than having a subnode named 'gpio'.
> 
> Initially, I did the same thing for both DT and ACPI, but Andy S.
> directed that ACPI should not have the node be shared in that way.
> 
> With the last revision of this patch, Andy S. asked that I try to get a
> rationalle from Rob (or other DT expert presumably) on why the gpio node
> should be combined with the parent, rather than being a named subnode
> [2].
> 
> Any context you can provide would be extremely helpful. Apologies about
> the age of this patch series and the amount of historical context; some
> is due to my long delays between revisions, but other of it is due to
> attempting to get the ACPI and DT folks to talk / agree.

I think this is about markers such as "gpio-controller" or
"interrupt-controller" in DT for the device in question.
With that it might not be required to have a separate child
node for the GPIO function.

> [1]: https://lore.kernel.org/all/20240213152825.GA1223720-robh@kernel.org/
> [2]: https://lore.kernel.org/all/aSdvv3Qss5oz_o6P@smile.fi.intel.com/

-- 
With Best Regards,
Andy Shevchenko