Re: USBDeviceOpen eventually returns kIOReturnExclusiveAccess
Re: USBDeviceOpen eventually returns kIOReturnExclusiveAccess
- Subject: Re: USBDeviceOpen eventually returns kIOReturnExclusiveAccess
- From: Doug Wyatt <email@hidden>
- Date: Thu, 27 Sep 2001 22:58:19 -0400
Is Classic running?
If so, it will grab your USB device since MIDI drivers are really just
user-side plug-ins, not kernel drivers.
10.1 has some mechanisms to work around this, although I haven't used
them personally. Also, a revised set of MIDI sample driver source will
follow, hopefully before long -- so it will be helpful for you to keep
track of any changes you make to the older sample driver source.
Doug
On Thursday, September 27, 2001, at 08:16 , Pete Gontier wrote:
I'm revising a USB MIDI plug-in which is based on the Apple sample code.
USBDeviceScanner::ScanDevices fails when USBDeviceOpen returns
kIOReturnExclusiveAccess, "exclusive access and device already open".
If this error occurred every time, I'd think some other part of my code
had
opened the device and forgotten to close it, perhaps on a previous
instantiation. But I'm pretty sure that's not the case, because this
code
does work for a while after boot, but stops working after a few
instantiations (on the order of 3 to 6). After that, I can reboot to
make it
start working again. Weird.
I'm running 10.0.4 vanilla on a G4 tower (part M5183) and using the
PlayNotes sample to test.
Any ideas what to look for? I know very little about what I'm doing
here,
but have some experience with OMS and USB under 9, if that makes any
difference.
--
Pete Gontier -- pete at midiman dot net -- <http://www.midiman.net/>
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Doug Wyatt
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personal: email@hidden
http://www.sonosphere.com
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