linux-kernel - Re: Build error on -next due to tpm

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Message-ID: <20250311211700.bwizwecxyxorrwql@bogus>
Date: Tue, 11 Mar 2025 21:17:00 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Stuart Yoder <stuart.yoder@....com>
Cc: Thorsten Leemhuis <linux@...mhuis.info>, jarkko@...nel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	lenb@...nel.org, rafael@...nel.org, jgg@...pe.ca, peterhuewe@....de,
	linux-integrity@...r.kernel.org,
	Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: Build error on -next due to tpm_crb.c changes?

On Tue, Mar 11, 2025 at 01:25:50PM -0500, Stuart Yoder wrote:
> 
> 
> On 3/11/25 11:51 AM, Thorsten Leemhuis wrote:
> > On 11.03.25 16:53, Stuart Yoder wrote:
> > > On 3/11/25 10:21 AM, Thorsten Leemhuis wrote:
> > > > On 05.03.25 18:36, Stuart Yoder wrote:
> > > [...]
> > > So, it should not be possible on one had have
> > > CONFIG_TCG_ARM_CRB_FFA being true when building tpm_crb.c
> > > and false resulting in the tpm_crb_ffa.o not being
> > > picked up in the build.
> > 
> > Many thx for the answer. Maybe Fedora's way to prepare the .config files
> > (which my package builds use to be close to Fedora's official packages)
> > is doing something odd/wrong. Will take a closer look and report back.
> 
> I've been experimenting with some different build config combinations
> and have reproduced what must be the issue.
> 
> This works fine:
> <*>   TPM 2.0 CRB Interface                                         < >
> TPM CRB over Arm FF-A Transport
> 
> This works fine:
> < >   TPM 2.0 CRB Interface                                         <*>
> TPM CRB over Arm FF-A Transport
> 
> This works fine:
> <*>   TPM 2.0 CRB Interface                                         <*>
> TPM CRB over Arm FF-A Transport
> 
> This works fine:
> <M>   TPM 2.0 CRB Interface                                         <M>
> TPM CRB over Arm FF-A Transport
> 
> This fails:
> <*>   TPM 2.0 CRB Interface                                         <M>
> TPM CRB over Arm FF-A Transport
> 
> The 2 drivers are coupled, so we can't have one built as a module
> and the other built-in.
> 
> I'm not a Kconfig expert, and need to do some fiddling to see
> if I can find a Kconfig syntax that prevents that failure scenario.
> 

	default y if (TCG_CRB && ARM_FFA_TRANSPORT)

is the issue here. You can select it as built-in if either or one of the
TCG_CRB and ARM_FFA_TRANSPORT is a module, but that is exactly what happens.
Not sure if default value is a must for you. But just depends on each of
these should be good enough and enable it in defconfig if needed. Or
you can have multiple default at least 4 combinations I can see. Both
are =y and either and both are =m

--
Regards,
Sudeep