linux-kernel - Re: [PATCH 00/18] Make common x86 arch area for i386 and x86_64

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Date:	Wed, 14 Mar 2007 14:41:12 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Glauber de Oliveira Costa <glommer@...il.com>
Subject: Re: [PATCH 00/18] Make common x86 arch area for i386 and x86_64 - Take 2


* Steven Rostedt <rostedt@...dmis.org> wrote:

> > i agree. We've recently factored out quite a bit of common code 
> > between i386 and x86_64 recently: genirq, gtod/clocksource and 
> > clockevents.
> 
> But those are things that can mostly be shared across all archs.

yeah.

> > and that's how i think unification of architectures should be done: 
> > move code into kernel/* and drivers/*, _not_ into another 
> > architecture. That way all architectures benefit.
> 
> I'm OK with it, although I did waste a lot of effort making those 
> patches (But I speak better in C than in English, or any other verbal 
> language, so it wasn't that bad). But if you look at the code that was 
> merged, I'm not sure many other archs will benefit. How many archs use 
> mtrr's? Perhaps these still can go into the drivers directory with a 
> bit of work. Don't know, I'm not that close to that code to be sure, 
> and don't have the time to find out ATM.

hm. Do you have any numbers handy - what is the end-result of your 
unification work, how many lines of code were unified, compared to the 
total body of code in i386 and x86_64?

> But at least there needs to be a more common way to share files 
> between the two archs. Having a file with just a single line of:
> 
> #include "../../i386/kernel/mycommoncode.c"
> 
> is not that elegant. The make files are, perhaps, a bit better.

yeah, that #include file thing for early_printk.c is just gross.

> Another thing that happens a lot with these shared funcs in these 
> files, is finding them . Since "make TAGS" doesn't bother to check 
> i386 when run with ARCH=x86_64. The first time I searched for 
> early_printk while developing i386 took me an hour, since my search 
> scripts don't check other archs (I've changed that since).  I thought 
> that the function was one of these macro created functions, and was 
> non-arch specific (didn't look into arch).
> 
> So, when creating new shared code, what's the "proper" way?

symbolic links perhaps? In that case i'd also introduce a common naming 
scheme: x86_early_printk.c - to make sure we know it right away that 
those files are bi-arch.

	Ingo
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