Re: Plugin loading and unloading

[Marcel Holtmann <marcel@holtmann.org>]

Hi Jaroslav,

> > I am working again on the A2DP Bluetooth plugin and the caching support
> > in the latest ALSA library is nice and allows me to keep the underlaying
> > link connected while stupid programs like XMMS closes the PCM when they
> > switch the tracks.
> > 
> > The PCM opening part and reusing of the underlaying AVDTP connection is
> > easy, but I am a little bit concerned about the plugin unloading time.
> > So is it possible to add init() and exit() functions that are called
> > when the plugin is loaded and unloaded. Like we have for kernel modules?
> 
> Wouldn't be possible to use ((constructor)) and ((destructor)) function 
> attributes for this purpose?

I have no idea how. Do you have an example for me. I like to try it.

> > Do the ALSA library has a timer mechanism that we can use inside a
> > plugin. Since it is a bad idea to hold the Bluetooth connection open for
> > all the time, I like to add a idle timeout. This allows me to put the
> > connection into sniff mode to save power or terminate it.
> 
> It's not possible to use any time resource using signals, because 
> applications might be using the signal for another purpose. It seems
> to me that the only possibility is to use fork() and code a little 
> watchdog or use threads.

I thought so for the signals, but can't ALSA provide somekind of other
timer mechanism for internal use?

> > Also the listing of plugins is still missing. I am fine with a general
> > or plugin specific flag to make its PCM visible.
> 
> Yes, I was evaluating all possibilities and the result is that we will 
> have a cache (configuration file) listing device names with short comments 
> which applications should offer to users in their GUI.
> 
> In this case, a configuration tool (alsactl as standard ALSA tool or 
> perhaps distribution specific) will check the installed and active plugins
> and create a list automagically which can be altered with advanced users
> later. Of course, the list won't be complete in any way, because 
> there are unlimited variations of virtual device names.

This looks fine to me. Will it in the 1.0.9 release?

Regards

Marcel




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