linux-kernel - Re: [PATCH 1/1] intel_txt: to fix build errors of CONFIG_ACPI

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Message-ID: <4A842C5B.7050100@zytor.com>
Date:	Thu, 13 Aug 2009 08:08:11 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	"Wang, Shane" <shane.wang@...el.com>,
	"Cihula, Joseph" <joseph.cihula@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"chrisw@...s-sol.org" <chrisw@...s-sol.org>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"jbeulich@...ell.com" <jbeulich@...ell.com>,
	"peterm@...hat.com" <peterm@...hat.com>,
	"Wei, Gang" <gang.wei@...el.com>
Subject: Re: [PATCH 1/1] intel_txt: to fix build errors of CONFIG_ACPI_SLEEP

On 08/12/2009 11:46 PM, Ingo Molnar wrote:
> * Wang, Shane <shane.wang@...el.com> wrote:
> 
>> Signed-off-by: Shane Wang <shane.wang@...el.com>
>>
>> diff -r 7358cf1b3090 arch/x86/kernel/tboot.c
>> --- a/arch/x86/kernel/tboot.c   Wed Aug 12 03:04:23 2009 -0700
>> +++ b/arch/x86/kernel/tboot.c   Wed Aug 12 18:06:21 2009 -0700
>> @@ -169,6 +169,7 @@ void tboot_create_trampoline(void)
>>
>>  static void set_mac_regions(void)
>>  {
>> +#ifdef CONFIG_ACPI_SLEEP
>>         tboot->num_mac_regions = 3;
>>         /* S3 resume code */
>>         tboot->mac_regions[0].start = PFN_PHYS(PFN_DOWN(acpi_wakeup_address));
>> @@ -181,6 +182,7 @@ static void set_mac_regions(void)
>>         tboot->mac_regions[2].start = PFN_PHYS(PFN_DOWN(virt_to_phys(&_text)));
>>         tboot->mac_regions[2].size = PFN_PHYS(PFN_UP(virt_to_phys(&_end))) -
>>                                      PFN_PHYS(PFN_DOWN(virt_to_phys(&_text)));
>> +#endif
> 
> These #ifdefs are quite ugly. Why not add a 'depends on ACPI_SLEEP' 
> rule to the INTEL_TXT Kconfig section?

I *strongly* disagree with that kind of false dependencies.  It makes it
seem like there is something magic going on, which invites cargo cult
programming in the future.  I also think those particular #ifdefs are
fairly innocuous... it's not like they're hiding flow of control or
major chunks of code.

However, I think the actual code to set the sections is ugly as hell,
which is probably why the #ifdef sticks in your eyes.

Consider the attached instead patch, which abstracts some of the (way
more complex than it should be) open-coded stuff and therefore makes it
stick out less.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.


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