Re: USBDeviceOpen eventually returns kIOReturnExclusiveAccess
Re: USBDeviceOpen eventually returns kIOReturnExclusiveAccess
- Subject: Re: USBDeviceOpen eventually returns kIOReturnExclusiveAccess
- From: Pete Gontier <email@hidden>
- Date: Fri, 28 Sep 2001 09:41:30 -0700
The problem turned out to be that Classic was running. I should have
realized this sooner. I imagine this problem comes up on this list about
every 5 seconds. My apologies.
circa 9/27/01 7:58 PM, Doug Wyatt <email@hidden> wrote:
>
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
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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
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>
>
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
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> PlayNotes sample to test.
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>
>
> Any ideas what to look for? I know very little about what I'm doing
>
> here,
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> 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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>
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>
>
>
>
--
>
Doug Wyatt
>
work: email@hidden (CoreAudio)
>
personal: email@hidden http://www.sonosphere.com
>
>
"It's kind of fun to do the impossible."
>
-- Walt Disney
>
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--
Pete Gontier -- pete at midiman dot net -- <
http://www.midiman.net/>