Date: Mon, 23 Jun 2008 20:45:37 +0300
From: Adrian Bunk <bunk@kernel.org>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Andi Kleen <andi@firstfloor.org>, David Woodhouse <dwmw2@infradead.org>,
       Tim Bird <tim.bird@am.sony.com>, torvalds@linux-foundation.org,
       akpm@linux-foundation.org,
       Paul Gortmaker <paul.gortmaker@windriver.com>,
       linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/1] Embedded Maintainer(s), linux-embedded@vger list
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On Mon, Jun 23, 2008 at 07:28:09PM +0200, Denys Vlasenko wrote:
> On Thursday 01 May 2008 12:41, Andi Kleen wrote:
> > > To a large extent, I agree. I certainly don't want to focus solely on
> > > code size; there's a lot more to embedded Linux than that. But it _is_
> > 
> > Not only code size, far more important is dynamic memory consumption.
> > [admittedly we right now lack a good instrumentation framework for this]
> > 
> > > There are some cases where we really _do_ want to have CONFIG options,
> > > but I agree that we should keep them to a minimum. And when we _do_ have
> > > CONFIG options, they don't have to litter the actual code with ifdefs.
> > 
> > The problem I see is more that really nobody can even compile not 
> > alone test all these combinations anymore. Hidding the problem in inlines
> > does not solve that. And no randconfig is not the solution either.
> 
> Because we allowed kernel to be developed without the requirement that
> random config should be buildable for release kernels.
> 
> Had it been a requirement, keeping it in shape wouldn't be
> too difficult.
> 
> Sure enough, _now_ fixing kernel to pass such a test on i386
> would take several weeks of work at least. But it is doable.
>...

On i386 it might even already work today.

But guess how much time it costs to get at least all defconfigs 
compiling on the other 22 architectures.

Even getting allmodconfig/allyesconfig compiling isn't trivial for all 
architectures, and random configurations are _far_ from compiling.

And we are not talking about something to be done once, as soon as you 
leave x86 there are tons of regular breakages.

Plus the fact that you often get into situations where more options
mean complex and fragile stuff. Read the Kconfig files under 
drivers/media/ and check in git all commits to them since 2.6.25 alone, 
and you'll understand why "add an option for every bit" can result in
very high ongoing maintainance work required.

Not everything that is technically possible is also maintainable, and 
maintainability is a very important point in a project with several 
million lines changing each year.

> vda

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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