Date: Sun, 21 Oct 2007 20:14:16 -0700
From: Randy Dunlap <rdunlap@xenotime.net>
To: Randy Dunlap <rdunlap@xenotime.net>
Cc: Sam Ravnborg <sam@ravnborg.org>, Henrik Carlqvist <hc1@poolhem.se>,
       linux-kernel@vger.kernel.org, bunk@stusta.de
Subject: Re: tristate and bool not enogh for Kconfig anymore
Message-Id: <20071021201416.4ccde183.rdunlap@xenotime.net>
In-Reply-To: <20071021174748.92abc989.rdunlap@xenotime.net>
References: <200710201257.55616.nick@ukfsn.org>
	<20071020144238.4f258c8c.hc1@poolhem.se>
	<20071020191700.GB8774@uranus.ravnborg.org>
	<26703.1192942058@turing-police.cc.vt.edu>
	<20071021122402.2f0f3b40.hc1@poolhem.se>
	<20071021094517.78dd1916.rdunlap@xenotime.net>
	<20071021210313.GA6725@uranus.ravnborg.org>
	<20071021174748.92abc989.rdunlap@xenotime.net>
Organization: YPO4
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2822
Lines: 77

On Sun, 21 Oct 2007 17:47:48 -0700 Randy Dunlap wrote:

> On Sun, 21 Oct 2007 23:03:13 +0200 Sam Ravnborg wrote:
> 
> > On Sun, Oct 21, 2007 at 09:45:17AM -0700, Randy Dunlap wrote:
> > > > Is there any other way to specify that a functionality can only be built
> > > > as a module, not built into the kernel?
> > > 
> > > config FOO
> > > 	depends on BAR && m
> > > 
> > > restricts FOO to module-only.
> > > 
> > > > In my firsta attempts to post about these tests my post ended up not on
> > > > the mailing list but as a reply to Sam Ravnborg only, apologies for
> > > > that...
> > 
> > This is obviously the right solution.
> > Randy - we should document this somewhere together with more kconfig tips'n'tricks.
> 
> Agreed.

So that's one tip or trick... or common idiom.

> > A new document or do we extend kconfig-language?
> 
> I don't see a need for a separate document.  I would just extend
> kconfig-language.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Another common idiom that we see (and sometimes have problems
with) is this:

When B (module or subsystem) uses interfaces from A (module or
subsystem), A can be linked statically into the kernel image or
can be built as loadable module(s).   This limits how B can be
built.  If A is linked statically into the kernel image, B can be
built statically or as loadable module(s).  However, if A is built
as loadable module(s), then B must be restricted to loadable
module(s) also.  This can be expressed in kconfig language as:

config B
	depends on A = y || A = B


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There's also a third issue:  symbols that are specific to a
particular $arch, but they are in Kconfig files that are common
to all arches, so kconfig complains about symbol A refers to
unknown symbol B.  (and I'm just writing this from memory, not
from testing it, so it could be off a bit.)  One example of this
was PS3_PS3AV, as copied from an lkml email of 2007-feb-14:

drivers/video/Kconfig:1604:warning: 'select' used by config symbol 
'FB_PS3' refer to undefined symbol 'PS3_PS3AV'

Someone fixed this one by introducing an intermediate config symbol.
I didn't follow the details of that fix, but we see this problem
enough to warrant explaining how to handle it.  E.g., recently
(from 2007-oct-14) on lkml:

$ make oldconfig >/dev/null
drivers/macintosh/Kconfig:121:warning: 'select' used by config 
symbol 'PMAC_APM_EMU' refers to undefined symbol 'APM_EMULATION'


Adrian, do you know of other items that should be listed here?

Thanks,
---
~Randy
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/