Re: External PCM plugin SDK

[Takashi Iwai <tiwai@suse.de>]

At Thu, 10 Feb 2005 20:04:30 +0100,
Marcel Holtmann wrote:
> 
> Hi Takashi,
> 
> > > > > > > The delayed close in the plugin is of course good to have.
> > > > > > > My only concern is that the code would be complicated to handle
> > > > > > > races.
> > > > > > 
> > > > > > actually I see a lifetime race inside the plugin if I try to handle it
> > > > > > by myself. When the close() callback is called, I must free all of my
> > > > > > allocated resources, because the shared object will be unloaded, right?
> > > > > 
> > > > > Yes, the close callback should clean up everything since there is no
> > > > > distinction between close and unload, so far.
> > > > 
> > > > if the ALSA core is not handling the XMMS behaviour for us, I really
> > > > need something to distinguish between close and unload.
> > > > 
> > > > What do you think about doing it like with kernel modules? Means we add
> > > > an init and an exit entry point inside the plugin. The rest is done via
> > > > callbacks. With this we should be able to register a PCM and also the
> > > > mixer controls for it within the same plugin.
> > > 
> > > That's a good idea.
> > 
> > ... and doesn't work as it is, unfortunately :-<
> > 
> > dlcose() is called after snd_pcm_close().
> > We may need to build object caches in alsa-lib.
> > This will improve the perfomance eventually, too.
> 
> questions is what will break if you change it. The only official plugin
> is the Jack plugin, right? So be bad and change this stuff and then fix
> the plugins.

The compatibility will be kept, I think.  Only the plugins with a
keep-alive flag are excluded from dlclose, and the objects are reused
at the next open.


Takashi


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