linux-kernel - Re: [PATCH 2/2] tpm: tpm_crb_ffa: maunally register tpm_crb

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Message-ID: <aEgiT8Pco-Cs8Kpa@kernel.org>
Date: Tue, 10 Jun 2025 15:17:19 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: sudeep.holla@....com, peterhuewe@....de, jgg@...pe.ca,
	stuart.yoder@....com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org
Subject: Re: [PATCH 2/2] tpm: tpm_crb_ffa: maunally register tpm_crb_ffa
 driver when it's built-in

On Fri, Jun 06, 2025 at 07:12:43PM +0100, Yeoreum Yun wrote:
> Hi Jarkko,
> 
> > > To integrate tpm_event_log with IMA subsystem,
> > > tpm_crb and tpm_crb_ffa driver should be built as built-in
> > > (CONFIG_TCG_CRB=y && CONFIG_TCG_CRB_FFA=y).
> > >
> > > However, this could make failure for ima_init() gets tpm chip when
> > > each initcall function deployed like:
> > >
> > > 0000000000000888 l       .initcall6.init	0000000000000000 crb_acpi_driver_init
> > > 000000000000088c l       .initcall6.init	0000000000000000 tpm_crb_ffa_driver_init
> >
> > The only failure I see is the patch 1/2 which changes init call level,
> > and leaves kernel Git to a broken state.
> >
> > It breaks the famous "zero regressions policy".
> >
> > BR, Jarkko
> 
> Sorry, would you let me know what is broken more detail?
> IMHO, by changing the init call level for ffa_init()
> it's called early than before device_initcall() and it seems not to
> break anything.
> 
> What breaks do you mean?

Let's start from very beginning. Why this change is needed and not just
1/2?

IMA intializes as a late initcall, which after TPM has initialized.

> 
> Thanks.
> 
> --
> Sincerely,
> Yeoreum Yun

BR, Jarkko