Re: alsa on non-linux

[Takashi Iwai <tiwai@suse.de>]

At Thu, 16 Jan 2014 13:27:17 +0000,
Patrick Welche wrote:
> 
> On Tue, Jan 14, 2014 at 03:04:58PM +0100, Clemens Ladisch wrote:
> > Patrick Welche wrote:
> > > I started out, writing the attached patch in November, but then it looked
> > > as though the boundaries of application library interface and linux sound
> > > chip driver had become so blurred that I thought that a decision had been
> > > taken to bin all OSes bar linux, hence the question. Can you give me a
> > > hint on how you think it is supposed to work?
> > 
> > Only the "hw" plugins access the Linux kernel drivers.  Anything else
> > should be portable (with the exception of plugins like "dmix" that
> > require a "hw" plugin as their slave).
> > 
> > For most device types (hwdep/seq/rawmidi/timer), the hw plugin is the
> > only implementation, so a portable alsa-lib has only control and pcm
> > devices at the moment.
> 
> So, rephrasing for the novice that I am, e.g., include/local.h contains
> 
> #include <endian.h>
> ...
> #if __BYTE_ORDER == __LITTLE_ENDIAN
> ...
> #include <linux/types.h>
> #include <linux/ioctl.h>
> 
> which are portability headaches. local.h is included by
> 
> src/alisp/alisp.c:#include "local.h"
> src/conf.c:#include "local.h"
> src/confmisc.c:#include "local.h"
> src/control/control_local.h:#include "local.h"
> src/control/namehint.c:#include "local.h"
> src/control/setup.c:#include "local.h"
> src/dlmisc.c:#include "local.h"
> src/error.c:#include "local.h"
> src/hwdep/hwdep_local.h:#include "local.h"
> src/input.c:#include "local.h"
> src/mixer/mixer_local.h:#include "local.h"
> src/names.c:#include "local.h"
> src/output.c:#include "local.h"
> src/pcm/pcm_local.h:#include "local.h"
> src/rawmidi/rawmidi_local.h:#include "local.h"
> src/seq/seq_event.c:#include "local.h"
> src/seq/seq_local.h:#include "local.h"
> src/seq/seq_midi_event.c:#include "local.h"
> src/seq/seq_old.c:#include "local.h"
> src/socket.c:#include "local.h"
> src/timer/timer_local.h:#include "local.h"
> src/ucm/ucm_local.h:#include "local.h"
> 
> That is fine except for files under directories src/control and src/pcm
> which ought to be portable? Or is it stronger, and everything should be
> portable except files under directory src/hwdep?

Why excluding hwdep...?  And, no, the codes have been written to be
portable, but the primary goal is a thin layer for Linux kernel ABI,
thus its support is the highest priority.

The linux/*.h file inclusions are basically for allowing to include
sound/asound.h as is.  It's a part of the Linux kernel code, and I
don't think we'd add any extra ifdefs there just for non-Linux.

IOW, you'd need to prepare some compatible defines before including
sound/asound.h if you need to compile for non-Linux systems.


Takashi