I have a usb composite device with 5 interfaces:
Interface 0 - bulk pipes
Interfaces 1-3 - Audio 2 class
Interface 4 - Midi class
Without loading third party kext this device operates as expected as a class
compliant audio/midi device. I want to create a kext which lays claim to the
Audio 2 class interfaces without hindering the operation of the Midi interface.
I have developed a kext whose IOKitPersonalities included a dictionary:
Device:
bInterfaceClass 1
bConfigurationValue 1
bInterfaceNumber 1 // this is the first
interface in the audio class
idProduct usb pid of device
idVendor usb vid of device
IOClass IOAudioDevice object from kext
(com_...)
IOProviderClass IOUSBInterface
I specified IOUSBInterface as the provider because I was only interested in a
subset of the composite device. When I loaded the kext it had no trouble
matching with the device and the start() and initHardware() methods of the
IOClass object get called. This object will use the IOService* provided to
find the other 2 interfaces associated with the audio function, create
IOAudioEngine and commence. I've been testing this on Yosemite and it seems to
work fine. The driver has no problem enumerating and opening the interfaces.
Enumerating the endpoints and streaming audio.
I run into a problem when I try to load this kext under El Capitan (10.11.4).
The kext seems to have trouble enumerating the interfaces past the first one.
The strange thing is that this doesn't fail 100% of the time. Maybe 5% of the
time when I load the kext it can enumerate all 3 interfaces. I thought maybe
it was some sort of timing issue, but I've made attempts with altered timing to
no avail.
I guess my question is: is there something wrong with matching an interface to
the driver object and expecting to be able to access the other interfaces in
the audio function? I need all 3 interfaces to run the audio and I link each
one to an independent IOService object in the driver and start/stop all of them.
===============================================================
Mike Horgan
Engineering
Line 6
O: 818.575.3670
H E L I X
Real. Smart. Control.
Helix is an entirely new kind of guitar processor. LEARN
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