linux-kernel - Re: [PATCH 9/9] x86/apic: support moorestown interrupt subsystem

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Date:	Mon, 29 Jun 2009 12:10:48 -0400 (EDT)
From:	Len Brown <lenb@...nel.org>
To:	Feng Tang <feng.tang@...el.com>
Cc:	"Pan, Jacob jun" <jacob.jun.pan@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"Brown, Len" <len.brown@...el.com>
Subject: Re: [PATCH 9/9] x86/apic: support moorestown interrupt subsystem

On Mon, 29 Jun 2009, Feng Tang wrote:

> On Sat, 27 Jun 2009 01:18:50 +0800
> "Pan, Jacob jun" <jacob.jun.pan@...el.com> wrote:
> 
> > >> -#ifdef CONFIG_ACPI
> > >> +#if defined(CONFIG_ACPI) || defined(CONFIG_SFI)
> > >
> > >Please add a new helper non-interactive Kconfig symbol instead of
> > >increasing the #ifdef jungle.
> > >
> > [[JPAN]] I agreed, maybe this should be part of the SFI patch or
> > already have similar plans?
> 
> Yes, Ingo has given similar comments for SFI code. I thought about 2
> methods for this:
> 1. these "#ifdef...#endif" covers three functions:
>  extern int io_apic_get_unique_id(int ioapic, int apic_id);
>  extern int io_apic_get_version(int ioapic);
>  extern int io_apic_get_redir_entries(int ioapic);	
> how about just completely removing the "#ifdef...#endif", as ACPI/SFI 
> codes are heavily used on x86 platforms, and it may bring one hundred
> additional bytes for None-ACPI/SFI platforms 
> 2. create a new "CONFIG_ACPI_SFI" option, using this new option to cover
> this case, and let "ACPI"/"SFI" option select it in Kconfig files
> 
> any comments? thanks

I vote #2 -- remove the #ifdefs.
All of these routines are both small and __init,
and the only build that would notice the extra bytes in .text
is the x86 IOAPIC ACPI=n build, which is uncommon today
and becoming more uncommon over time.

The SFI patch series doesn't actually depend on these routines,
the IO-APIC patch depends on them.  So this change
should be in the IO-APIC series.

cheers,
-Len Brown, Intel Open Source Technology Center
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