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

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Date:	Tue, 20 Oct 2015 17:58:35 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Andreas Ziegler <andreas.ziegler@....de>
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

On Tue, Oct 20, 2015 at 01:49:02PM +0200, Andreas Ziegler wrote:
> 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?

Good catch. Shoud I send a separate fix for this? Thanks for pointing
this out.

> Regards,
> 
> Andreas
> 
> [0] https://cados.cs.fau.de

/Jarkko
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