Re: [Jack-Devel] Jack2 alsarawmidi slave: Pluggable device registration problem?

On October 2, 2014 12:27:28 PM Devin Anderson wrote:
> Hi Tim,
> 
> On Sat, Sep 27, 2014 at 4:47 PM, Tim E. Real <[hidden]> wrote:
> > When I plug in my USB midi device after starting Jack2 with alsarawmidi,
> > 
> >  it does not register at all, as jack_lsp shows.
> 
> That's because the driver doesn't detect new devices.  It looks at the
> devices that are connected when you start JACK, and assumes that those
> are the devices that will be used.  I took this approach when I wrote
> the driver because, at the time (it may still be this way), there
> wasn't an elegant way to detect new devices using ALSA's rawmidi
> interface.  I believe the ALSA sequencer interface has an event
> mechanism for new devices; the rawmidi interface, in contrast, has no
> such mechanism.
> 
> > But then if I unplug the device, strangely the ports do not unregister and
> > I can even make connections to them in qjctl.
> 
> I'm not surprised that the ports don't disappear, but I am surprised
> that there isn't a bunch of (poll-related) error messages that flood
> your JACK console.
> 
> I'm happy to help brainstorm on ideas about how to best solve the
> problem.  I can't guarantee that I'll find time to actually fix the
> problem if and when a reasonable solution pops up.
> 
> Thanks,


Greetings Devin! Thanks for replying.

As Dan mentions, we are keen to finish this driver because it,
 along with the corresponding alsamidi Jack1 driver, is being touted
 as the replacement for the raw and seq drivers.

(Sadly the a2jmidid project doesn't compile any more because of the 
 infamous compiler library linking ordering switcheroo which
 happened a few years ago - libraries must now come at the end.
There is a recent August bug report filed there. Hope Nedko sees it.)

Devin, the old raw driver seems to detect and remove devices just fine.
Is there something that would not be right, some ugliness, in using that 
 existing code?

I looked at the code in the old raw driver and this newer one.
I /think/ I might be able to try it, no stranger to alsa here, but the two
 code bases are quite different, I'm not sure where to 'put' any new stuff.

Thanks.
Tim.

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