[alsa-devel] usr/include/linux/soundcard.h warnings for 'make headers_check'

[Takashi Iwai]

At Wed, 4 Feb 2009 13:51:17 +0100,
Arnd Bergmann wrote:
> 
> On Wednesday 04 February 2009, Takashi Iwai wrote:
> 
> > It's not always true -- that's the whole problem I'm concerned.
> > Apparently old apps do include linux/soundcard.h.
> > 
> > I agree to remove the stuff causing warnings, i.e. moving oss-lib part
> > to sys/soundcard.h.  In this case, the only possible regression is the
> > case where apps use OSS-lib and include linux/soundcard.h.  For other
> > cases (use sequencer stuff with linux/soundcard.h but without
> > oss-lib), it will still work.
> 
> You cannot "move" things to <sys/soundcard.h>, because that file
> is provided by glibc as a simple redirect to <linux/soundcard.h>.
> The problem there is obviously the compatibility of combinations
> of kernel and glibc before and after the change.

Ah right.

> The use cases I can see include:
> 
> 1. A simple app that only needs the ioctl definitions in
>    linux/soundcard.h and does not care about all this.
> 
> 2. A slightly more sophisticated app that uses the !OSSLIB part of
>    <sys/soundcard.h> or <linux/soundcard.h>.
> 
> 3. A new OSSlib application for OSS-3.9 or OSS-4.x that uses the
>    <sys/soundcard.h> file provided by OSSlib, instead of the
>    one from glibc.
> 
> 4. A legacy OSSlib application from the last century using either
>    linux/soundcard.h or sys/soundcard.h to get at the macros.
> 
> 5. An application that gets compiled against <linux/soundcard.h>
>    but linked against OSSlib 3.9 or 4.x.
> 
> Removing the macros and extern declarations from linux/soundcard.h
> will break the final two cases. The only options I can see here
> are "do nothing" and "screw them". 
> Both should be fine, because the warning is easy to shut up
> with a small preprocessor macro #define _SEQ_EXTERN extern,
> and it's rather unlikely that anyone runs into this problem
> on a 2.6 kernel in the first place.
> 
> 	Arnd <><
> 
> ---
> This patch breaks building against OSSlib with the kernel headers
> instead of its own headers. It should still work with any
> version of the library from the 2003 onwards which provide
> their own headers for the latest interface.
> 
> Signed-off-by: Arnd Bergmann <arnd at arndb.de>

The patch looks reasonable to me.

Acked-by: Takashi Iwai <tiwai at suse.de>

Or, I'll include the patch later to sound git tree unless any
objection comes up.


thanks,

Takashi

> 
> --- a/include/linux/soundcard.h
> +++ b/include/linux/soundcard.h
> @@ -1045,7 +1045,7 @@ typedef struct mixer_vol_table {
>   */
>  #define LOCL_STARTAUDIO		1
>  
> -#if (!defined(__KERNEL__) && !defined(KERNEL) && !defined(INKERNEL) && !defined(_KERNEL)) || defined(USE_SEQ_MACROS) 
> +#if !defined(__KERNEL__) || defined(USE_SEQ_MACROS)
>  /*
>   *	Some convenience macros to simplify programming of the
>   *	/dev/sequencer interface
> @@ -1056,39 +1056,15 @@ typedef struct mixer_vol_table {
>  
>  void seqbuf_dump(void);	/* This function must be provided by programs */
>  
> -extern int OSS_init(int seqfd, int buflen);
> -extern void OSS_seqbuf_dump(int fd, unsigned char *buf, int buflen);
> -extern void OSS_seq_advbuf(int len, int fd, unsigned char *buf, int buflen);
> -extern void OSS_seq_needbuf(int len, int fd, unsigned char *buf, int buflen);
> -extern void OSS_patch_caching(int dev, int chn, int patch,
> -			      int fd, unsigned char *buf, int buflen);
> -extern void OSS_drum_caching(int dev, int chn, int patch,
> -			      int fd, unsigned char *buf, int buflen);
> -extern void OSS_write_patch(int fd, unsigned char *buf, int len);
> -extern int OSS_write_patch2(int fd, unsigned char *buf, int len);
> -
>  #define SEQ_PM_DEFINES int __foo_bar___
> -#ifdef OSSLIB
> -#  define SEQ_USE_EXTBUF() \
> -		extern unsigned char *_seqbuf; \
> -		extern int _seqbuflen;extern int _seqbufptr
> -#  define SEQ_DEFINEBUF(len) SEQ_USE_EXTBUF();static int _requested_seqbuflen=len
> -#  define _SEQ_ADVBUF(len) OSS_seq_advbuf(len, seqfd, _seqbuf, _seqbuflen)
> -#  define _SEQ_NEEDBUF(len) OSS_seq_needbuf(len, seqfd, _seqbuf, _seqbuflen)
> -#  define SEQ_DUMPBUF() OSS_seqbuf_dump(seqfd, _seqbuf, _seqbuflen)
> -
> -#  define SEQ_LOAD_GMINSTR(dev, instr) \
> -		OSS_patch_caching(dev, -1, instr, seqfd, _seqbuf, _seqbuflen)
> -#  define SEQ_LOAD_GMDRUM(dev, drum) \
> -		OSS_drum_caching(dev, -1, drum, seqfd, _seqbuf, _seqbuflen)
> -#else /* !OSSLIB */
> -
> -#  define SEQ_LOAD_GMINSTR(dev, instr)
> -#  define SEQ_LOAD_GMDRUM(dev, drum)
> -
> -#  define SEQ_USE_EXTBUF() \
> -		extern unsigned char _seqbuf[]; \
> -		extern int _seqbuflen;extern int _seqbufptr
> +
> +#define SEQ_LOAD_GMINSTR(dev, instr)
> +#define SEQ_LOAD_GMDRUM(dev, drum)
> +
> +#define _SEQ_EXTERN extern
> +#define SEQ_USE_EXTBUF() \
> +		_SEQ_EXTERN unsigned char _seqbuf[]; \
> +		_SEQ_EXTERN int _seqbuflen;_SEQ_EXTERN int _seqbufptr
>  
>  #ifndef USE_SIMPLE_MACROS
>  /* Sample seqbuf_dump() implementation:
> @@ -1131,7 +1107,6 @@ extern int OSS_write_patch2(int fd, unsigned char *buf, int len);
>   */
>  #define _SEQ_NEEDBUF(len)	/* empty */
>  #endif
> -#endif /* !OSSLIB */
>  
>  #define SEQ_VOLUME_MODE(dev, mode)	{_SEQ_NEEDBUF(8);\
>  					_seqbuf[_seqbufptr] = SEQ_EXTENDED;\
> @@ -1215,14 +1190,8 @@ extern int OSS_write_patch2(int fd, unsigned char *buf, int len);
>  		_CHN_COMMON(dev, MIDI_CHN_PRESSURE, chn, pressure, 0, 0)
>  
>  #define SEQ_SET_PATCH SEQ_PGM_CHANGE
> -#ifdef OSSLIB
> -#   define SEQ_PGM_CHANGE(dev, chn, patch) \
> -		{OSS_patch_caching(dev, chn, patch, seqfd, _seqbuf, _seqbuflen); \
> -		 _CHN_COMMON(dev, MIDI_PGM_CHANGE, chn, patch, 0, 0);}
> -#else
> -#   define SEQ_PGM_CHANGE(dev, chn, patch) \
> +#define SEQ_PGM_CHANGE(dev, chn, patch) \
>  		_CHN_COMMON(dev, MIDI_PGM_CHANGE, chn, patch, 0, 0)
> -#endif
>  
>  #define SEQ_CONTROL(dev, chn, controller, value) \
>  		_CHN_COMMON(dev, MIDI_CTL_CHANGE, chn, controller, 0, value)
> @@ -1300,19 +1269,12 @@ extern int OSS_write_patch2(int fd, unsigned char *buf, int len);
>  /*
>   * Patch loading.
>   */
> -#ifdef OSSLIB
> -#   define SEQ_WRPATCH(patchx, len) \
> -		OSS_write_patch(seqfd, (char*)(patchx), len)
> -#   define SEQ_WRPATCH2(patchx, len) \
> -		OSS_write_patch2(seqfd, (char*)(patchx), len)
> -#else
> -#   define SEQ_WRPATCH(patchx, len) \
> +#define SEQ_WRPATCH(patchx, len) \
>  		{if (_seqbufptr) SEQ_DUMPBUF();\
>  		 if (write(seqfd, (char*)(patchx), len)==-1) \
>  		    perror("Write patch: /dev/sequencer");}
> -#   define SEQ_WRPATCH2(patchx, len) \
> +#define SEQ_WRPATCH2(patchx, len) \
>  		(SEQ_DUMPBUF(), write(seqfd, (char*)(patchx), len))
> -#endif
>  
>  #endif
>  #endif
>