linux-kernel - Re: [PATCH v9 2/2] usb: dwc3: Add Google Tensor SoC DWC3 glue driver

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Message-ID: <2025121847-swifter-pug-a1f7@gregkh>
Date: Thu, 18 Dec 2025 07:27:33 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Roy Luo <royluo@...gle.com>
Cc: Doug Anderson <dianders@...gle.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Peter Griffin <peter.griffin@...aro.org>,
	André Draszik <andre.draszik@...aro.org>,
	Tudor Ambarus <tudor.ambarus@...aro.org>,
	Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Badhri Jagan Sridharan <badhri@...gle.com>,
	linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org,
	Joy Chakraborty <joychakr@...gle.com>,
	Naveen Kumar <mnkumar@...gle.com>
Subject: Re: [PATCH v9 2/2] usb: dwc3: Add Google Tensor SoC DWC3 glue driver

On Wed, Dec 17, 2025 at 05:34:37PM -0800, Roy Luo wrote:
> On Wed, Dec 17, 2025 at 12:14 PM Doug Anderson <dianders@...gle.com> wrote:
> >
> > Hi,
> >
> > On Wed, Dec 17, 2025 at 11:18 AM Roy Luo <royluo@...gle.com> wrote:
> > >
> > > On Wed, Dec 17, 2025 at 5:24 AM Greg Kroah-Hartman
> > > <gregkh@...uxfoundation.org> wrote:
> > > >
> > > > On Thu, Dec 04, 2025 at 11:14:39PM -0800, Roy Luo wrote:
> > > > > On Thu, Dec 4, 2025 at 10:05 PM Greg Kroah-Hartman
> > > > > <gregkh@...uxfoundation.org> wrote:
> > > > > >
> > > > > > On Fri, Dec 05, 2025 at 02:26:38AM +0000, Roy Luo wrote:
> > > > > > > +config USB_DWC3_GOOGLE
> > > > > > > +     tristate "Google Platform"
> > > > > > > +     depends on ARCH_GOOGLE || COMPILE_TEST
> > > > > >
> > > > > > There is no ARCH_GOOGLE in the tree now, so how is this supposed to
> > > > > > work?  Shouldn't tools that check for "invalid config options" trigger
> > > > > > on this?
> > > > > >
> > > > > > thanks,
> > > > > >
> > > > > > greg k-h
> > > > >
> > > > > Hi Greg,
> > > > >
> > > > > The menuconfig looks like the following and it doesn't complain:
> > > > > | Symbol: ARCH_GOOGLE [=ARCH_GOOGLE]
> > > > > | Type  : unknown
> > > > > |
> > > > > | Symbol: PHY_GOOGLE_USB [=y]
> > > > > | Type  : tristate
> > > > > | Defined at drivers/phy/Kconfig:104
> > > > > |     Prompt: Google Tensor SoC USB PHY driver
> > > > > |     Depends on: ARCH_GOOGLE || COMPILE_TEST [=y]
> > > > >
> > > > > According to Kconfig documentation [1], the unknown symbol
> > > > > would simply be evaluated as an "n", which is what we want.
> > > > > "Convert the symbol into an expression. Boolean and tristate
> > > > > symbols are simply converted into the respective expression
> > > > > values. All other symbol types result in ‘n’."
> > > > >
> > > > > In a different Kconfig documentation, an environment variable
> > > > > "KCONFIG_WARN_UNKNOWN_SYMBOLS" is there to detect
> > > > > undefined symbols in the "config input", but I can't find one that
> > > > > catches undefined symbols in the Kconfig tree itself.
> > > > >
> > > > > That is, the tool seems to allow this.
> > > > > However, if this turns out to be a major problem. I think we
> > > > > can either:
> > > > > - Remove ARCH_GOOGLE and leave COMPILE_TEST as
> > > > >   the only dependency. Then add ARCH_GOOGLE back
> > > > >   later once it's in the tree.
> > > >
> > > > Please do this.  I do not want to take patches that purposfully add
> > > > dependencies on config options that might, or might not, appear in the
> > > > future.  Please just remove all of the dependancies for now, as they are
> > > > not needed, right?
> > > >
> > > > thanks,
> > > >
> > > > greg k-h
> > >
> > > Greg,
> > >
> > > Yes, we can remove ARCH_GOOGLE for now.
> > > To clarify, we're not removing all of the dependencies, we still want
> > > to keep COMPILE_TEST for build tests, right?
> > > Please let me know if you think otherwise.
> >
> > I think you'd just remove all of them. Normally COMPILE_TEST just
> > allows folks to compile stuff even when they don't want the ARCH. We
> > can can add ARCH_GOOGLE back in later once the config exists.
> >
> > -Doug
> 
> Doug,
> 
> Thanks for chiming in. I'm hesitant to remove COMPILE_TEST
> because Greg specifically requested its inclusion in v7 [1].
> Also it seems beneficial to get some build coverage before
> ARCH_GOOGLE is officially added to the tree.
> Greg, could you clarify?

I wanted it in because it would not build without it on a non "google"
system.  But now, as that option isn't there, just don't have any
dependency, as it's obviously not needed.

thanks,

greg k-h