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

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Message-ID: <CA+zupgyG4Nov0=jihSApp_3_0hy6YNZMkfOp6Q4-zmERFm10Ag@mail.gmail.com>
Date: Wed, 17 Dec 2025 17:34:37 -0800
From: Roy Luo <royluo@...gle.com>
To: Doug Anderson <dianders@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 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 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?

[1] https://lore.kernel.org/linux-usb/2025112144-claw-recolor-49c3@gregkh/

Thanks,
Roy