Date: Mon, 19 Jun 2006 13:46:48 +0200 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-multimedia@freebsd.org Subject: Complaints about the sound system with regard to USB Message-ID: <200606191346.48853.hselasky@c2i.net>
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Hi,
I have some complaints about the sound system with regard to USB.
1) If you are playing sound, and unplug the sound device, the system is going
to come down with a panic, hence "pcm_unregister()" returns EBUSY, and that
is not allowed when a USB device is detached.
2) The locking system is not right. Why must the sound device driver unlock
its private lock before calling "chn_intr()" ? I see why, because else you
get a dead lock:
if (ch->run) {
ICH_UNLOCK(sc);
chn_intr(ch->channel);
ICH_LOCK(sc);
}
Solution:
1) It is not impossible to kill opened devices at detach.
2) Please use only one lock per "sound-controller". All "child" structures
should be protected by this lock, PCM, MIDI, whatever. And when you call up,
lock this lock before doing the call, ala CHN_LOCK(). And when you call down,
this lock should already be locked.
/*---------------------------------------------------------------------------*
* pcm_controller_allocate
*
* NOTE: all sub-controllers are under the same lock!
*---------------------------------------------------------------------------*/
struct pcm_controller *
pcm_controller_allocate(u_int8_t portable, u_int8_t sub_controllers)
Any comments?
--HPS
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