From: Marcus Metzler <mocm@metzlerbros.de>
Message-ID: <16121.58735.59911.813354@sheridan.metzler>
Date: Wed, 25 Jun 2003 20:09:51 +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: <20030625185036.C29537@infradead.org>
References: <20030625160830.A19958@infradead.org>
	<20030625154223.GB1333@mars.ravnborg.org>
	<3EF9CB25.4050105@convergence.de>
	<16121.53934.527440.109966@sheridan.metzler>
	<20030625175513.A28776@infradead.org>
	<16121.55366.94360.338786@sheridan.metzler>
	<20030625181606.A29104@infradead.org>
	<16121.55873.675690.542574@sheridan.metzler>
	<20030625182409.A29252@infradead.org>
	<16121.56382.444838.485646@sheridan.metzler>
	<20030625185036.C29537@infradead.org>
Reply-To: mocm@mocm.de
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Christoph Hellwig writes:
 > On Wed, Jun 25, 2003 at 07:30:38PM +0200, Marcus Metzler wrote:
 > > Well, then you are wrong. You need those headers for user space
 > > applications and also for the kernel. The define the communication
 > > structures. If you put them into /usr/include you always risk having
 > > different versions of those structures. 
 > 
 > 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


typedef struct dvb_frontend_parameters {
        uint32_t frequency;       /* (absolute) frequency in Hz for QAM/OFDM */
                                  /* intermediate frequency in kHz for QPSK */
        fe_spectral_inversion_t inversion;
        union {
                struct dvb_qpsk_parameters qpsk;
                struct dvb_qam_parameters  qam;
                struct dvb_ofdm_parameters  ofdm;
        } u;
} dvb_frontend_params_t;

to
 

wtypedef struct dvb_frontend_parameters {
        uint32_t frequency;       /* (absolute) frequency in Hz for QAM/OFDM */
                                  /* intermediate frequency in kHz for QPSK */
        fe_spectral_inversion_t inversion;
        union {
                struct dvb_qpsk_parameters qpsk;
                struct dvb_qam_parameters  qam;
                struct dvb_ofdm_parameters  ofdm;
                struct dvb_xyz_parameters  xyz;
        } u;
} dvb_frontend_params_t;

won't change anything for user space apps. (We are only talking about
self compiled ones here anyway, otherwise you won't need the headers.) 

 > have a copy in /usr/include that you can upgrade without updating libc
 > also, that way you can at least get the new structures / defines in time.
 > 
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>. 
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. Distribution users won't compile anyway and if they do they
probably need to get a kernel.org kernel.

Marcus

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

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