Re: trying out usb hotplugs

[Takashi Iwai <tiwai@suse.de>]

At Fri, 29 Nov 2002 10:39:22 +0100 (CET),
Jaroslav wrote:
> 
> On Fri, 29 Nov 2002, Takashi Iwai wrote:
> 
> > At Fri, 29 Nov 2002 08:52:43 +0100 (MET),
> > Clemens Ladisch wrote:
> > > 
> > > Takashi Iwai wrote:
> > > > Martin Langer wrote:
> > > > > usb hotplug works perfect if my usbmidi client isn't aconnected to another
> > > > > midi client. But the aconnected usb midi device still remains in the clients
> > > > > list, after hotpluging out.
> > > >
> > > > yep,  when the connection exists, the connected devices (on both
> > > > sides) are regarded as active.
> > > 
> > > The sequencer design allows asynchronous removal of clients.
> > 
> > yes, but this may still try to send some bytes to the unplugged
> > rawmidi device at the disconnection.  i'll change rawmidi code to
> > ignore that.
> 
> Well, I'm trying to solve these "hotplug" problems. Unfortunately, it 
> seems difficult to detect, if another task is in the middle of our 
> callback. I think that we'll end up using mutexes.

hmm, but mutex costs too much even for non-pluggable devices...

in the case of rawmidi and oss-mixer, we can put "disconnected" flag
and ignore the access if the flag is on at the rawmidi and oss-mixer
routines, so that the control doesn't reach to low-level functions.

at least, the sequencer connection problem seems ok.
i'm checking now whether it can work for oss-mixer, too.


Takashi


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