linux-kernel - Re: tpm, tpm_tis: fix tpm_tis ACPI detection issue with TPM 2.0

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Message-ID: <56262A2E.6040602@fau.de>
Date:	Tue, 20 Oct 2015 13:49:02 +0200
From:	Andreas Ziegler <andreas.ziegler@....de>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	tpmdd-devel@...ts.sourceforge.net,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Valentin Rothberg <rothberg@...fau.de>,
	Paul Bolle <pebolle@...cali.nl>
Subject: Re: tpm, tpm_tis: fix tpm_tis ACPI detection issue with TPM 2.0

Hi Jarkko,

your patch "tpm, tpm_tis: fix tpm_tis ACPI detection issue with TPM 2.0"
showed up as commit 399235dc6e95 in linux-next today (that is,
next-20151020). I noticed it because we (a research group from
Erlangen[0]) are running daily checks on linux-next.

Your commit creates the following structure of #ifdef blocks in
drivers/char/tpm/tpm_tis.c following line 1088:

 #ifdef CONFIG_ACPI
 ...
 #ifdef CONFIG_PNP
 ...
 #endif
 ...
 #endif

Looking at the definition of CONFIG_ACPI at drivers/acpi/Kconfig, line
5, we see that ACPI unconditionally selects PNP, meaning that CONFIG_PNP
is always enabled if CONFIG_ACPI has been enabled.
Thus, the inner #ifdef statement can never evaluate to 'false' if the
outer #ifdef evaluates to true (i.e., CONFIG_ACPI is enabled), and
hence, the #ifdef is unnecessary.

The same situation holds for the nested structure following line 1124,
where the #ifdef CONFIG_PNP at line 1129 is unnecessary.

Is this correct or did we miss something?

Regards,

Andreas

[0] https://cados.cs.fau.de
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