linux-kernel - Re: [PATCH v3 00/14] Add support for handling PCIe M.2 Key E connectors in devicetree

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Message-ID: <CAMRc=MfoUi-qvZnOcM5pgvmVhPMEK+gvs5m2APrqLXc2J7x1AQ@mail.gmail.com>
Date: Mon, 12 Jan 2026 02:54:16 -0800
From: Bartosz Golaszewski <brgl@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Rob Herring <robh@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Jiri Slaby <jirislaby@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, Hans de Goede <hansg@...nel.org>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Mark Pearson <mpearson-lenovo@...ebb.ca>, "Derek J. Clark" <derekjohn.clark@...il.com>, 
	Manivannan Sadhasivam <mani@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Marcel Holtmann <marcel@...tmann.org>, Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
	Bartosz Golaszewski <brgl@...ev.pl>, Daniel Scally <djrscally@...il.com>, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Bartosz Golaszewski <brgl@...nel.org>, linux-serial@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	platform-driver-x86@...r.kernel.org, linux-pci@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	linux-bluetooth@...r.kernel.org, linux-pm@...r.kernel.org, 
	Stephan Gerhold <stephan.gerhold@...aro.org>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, linux-acpi@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Sui Jingfeng <sui.jingfeng@...ux.dev>, 
	manivannan.sadhasivam@....qualcomm.com
Subject: Re: [PATCH v3 00/14] Add support for handling PCIe M.2 Key E
 connectors in devicetree

On Mon, 12 Jan 2026 09:04:15 +0100, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> said:
> On Sat, Jan 10, 2026 at 12:26:18PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
>>

[snip]

>> Though this series adds the relevant functionality for handling the M.2 Key M
>> connectors, there are still a few open questions exists on the design.
>>
>> 1. I've used the DT compatible for the serdev swnode to match the existing OF
>> device_id of the bluetooth driver. This avoids implementing custom serdev id
>> matching as implemented till v2.
>
> Yeah, swnodes are not designed to replace the real DT or other firmware
> interface. The idea of swnodes is to have them providing quirks if needed (i.e.
> fixing up the broken or missed FW device properties). This should not have been
> done this way. Please, consider another approach, e.g. DT-overlay.
>

This may have been true historically but software nodes were introduced before
the auxiliary bus. With platform devices, the question has a clear response:
DT or ACPI first, then possibly additional software node. But with auxiliary
devices, where does the entirety of device properties come from if we - for
whatever reason - don't want to propagate any "real" firmware node?

This is not even about this particular series, rather it's a wider architecture
question.

Bartosz