linux-kernel - Re: Per option CFLAGS?

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Message-ID: <20070915155231.GU3563@stusta.de>
Date:	Sat, 15 Sep 2007 17:52:32 +0200
From:	Adrian Bunk <bunk@...nel.org>
To:	Rene Herman <rene.herman@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Kai Germaschewski <kai@...maschewski.name>,
	Sam Ravnborg <sam@...nborg.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	ALSA devel <alsa-devel@...a-project.org>
Subject: Re: Per option CFLAGS?

On Sat, Sep 15, 2007 at 05:17:08PM +0200, Rene Herman wrote:
> On 09/15/2007 10:47 AM, Adrian Bunk wrote:
>
>> On Sat, Sep 15, 2007 at 01:30:21AM +0200, Rene Herman wrote:
>>> On 09/15/2007 01:13 AM, H. Peter Anvin wrote:
>>>
>>>> Rene Herman wrote:
>>>>> I have a single file foo.c that I want to generate two (ALSA) modules
>>>>> from, snd-foo2000.ko and snd-foo2001.ko, by compiling with either
>>>>> FOO2000 or FOO2001 defined.
>>>>>
>>>>> I can do this, and ALSA does this a few times, by providing dummy
>>>>> foo2000.c and foo2001.c files, like:
>>>>>
>>>>> === foo2000.c
>>>>> #define FOO2000
>>>>> #include "foo.c"
>>>>> ===
>
> [ ... ]
>
>>>> The stub source file is usually considered a good way to do this.
>>> Mmm. If I'll have to live with it, I can, but thought I'd ask if there 
>>> was some nice build trickery available instead.
>> The usual trick is to create _three_ modules:
>> Two with the foo2000 and foo2001 specific parts, and a third one with all 
>> code used by both.
>> Or if foo2000 and foo2001 differ only in small details, create one 
>> snd-foo200x module supporting both at the same time.
>
> Thanks for the comment. Yes, first would be massive overkill in this case 
> and second somewhat annoying as one of the differences is support for 
> different resources (IRQs) among the two versions, whereas I'm checking the 
> validity of the passed in values at a time I do not know which version I'm 
> looking at yet -- knowing that requires having talked to the hardware.

I'm not getting this point.

Consider both snd-foo2000 and snd-foo2001 are compiled statically into 
the kernel - somehow one of them must realize quite early that it's not 
responsible for the device.

And however this is done, it should similarly work in one module 
supporting both.

> Can do, but for now it seems like the two seperate modules might be 
> cleaner. Can keep things much more straighforward that way by just 
> redefining a bunch of #defines.
>
> I'll just do the split version first and if someone really wants me to, 
> I'll merge them after all...
>
> Rene

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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