From: Marcus Metzler <mocm@metzlerbros.de>
Message-ID: <16121.60747.537424.961385@sheridan.metzler>
Date: Wed, 25 Jun 2003 20:43:23 +0200 (CEST)
To: Christoph Hellwig <hch@infradead.org>
Cc: mocm@mocm.de, Michael Hunold <hunold@convergence.de>,
       Sam Ravnborg <sam@ravnborg.org>, linux-kernel@vger.kernel.org
Subject: Re: DVB Include files
In-Reply-To: <20030625191532.A1083@infradead.org>
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Christoph Hellwig writes:
 > On Wed, Jun 25, 2003 at 08:09:51PM +0200, Marcus Metzler wrote:
 > >  > If the structures change incompatibly you're fucked anyway.  Better
 > > 
 > > Not necessarily, e.g. changing
 > > 
 > > #define AUDIO_SET_ATTRIBUTES       _IOW('o', 17, audio_attributes_t)
 > > #define AUDIO_SET_KARAOKE          _IOW('o', 18, audio_karaoke_t)
 > > 
 > > to 
 > > 
 > > #define AUDIO_SET_ATTRIBUTES       _IOW('o', 47, audio_attributes_t)
 > > #define AUDIO_SET_KARAOKE          _IOW('o', 48, audio_karaoke_t)
 > > 
 > > or
 > 
 > In that case yes, you are screwed.  Your ABI just changed incompatibly.

Not if you recompile.

 > 
 > > Anyway, even in user/include it should be under linux/dvb because
 > > that's just what it is Linux DVB. So the app has to include
 > > <linux/dvb/xxx.h>. 
 > 
 > No!  <linux/*.h> is the namesapce for kernelheaders.  Currently they're
 > still in the the user includes, too (due to legacy reasons).  The
 > DVD API must move to a directory outside <linux/dvb>.
 > 

Why (It's DVB by the way)? It's as close to the kernel as ls or cat
and having two sets of the same includes is stupid. 

 > If you userland packages add headers to /usr/include/linux/ they
 > are totally bogus.
 > 

What packages? You are always talking about packages. There are no packages.
There are only the kernel and my app. Nothing else. No copying of headers.

 > > I don't care what distributions do. When I get a new kernel (no
 > > packages), I use the includes from that kernel and compile my apps
 > > with that.
 > 
 > And that's wrong.  You must always compile against the kernel headers
 > that your libc was compiled against.
 > 

There is no one who does that, not even distributions. The includes
needed for libc are far less prone to change than v4l or dvb. And not
as linux specific.

I see your point, but right now it's only academic and not practicable.

Marcus

-- 
/--------------------------------------------------------------------\
| Dr. Marcus O.C. Metzler        |                                   |
|--------------------------------|-----------------------------------|
| mocm@metzlerbros.de            | http://www.metzlerbros.de/        |
\--------------------------------------------------------------------/

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