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Re: USB Audio driver and THREAD_TIME_CONSTRAINT_POLICY

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Re: USB Audio driver and THREAD_TIME_CONSTRAINT_POLICY

Subject: Re: USB Audio driver and THREAD_TIME_CONSTRAINT_POLICY
From: Vyacheslav Matyushin <email@hidden>
Date: Wed, 28 Dec 2011 03:24:33 -0800 (PST)

Just in case anybody face strange gaps in buffers used with IOUSBLowLatencyIsocFrame,
allocate memory for them using this pattern (add sanity checks):

mach_vm_address_t physicalMask;
IOOptionBits usbOptions;
IOUSBControllerV2 *usbController;

usbController = OSDynamicCast(IOUSBControllerV2, mStreamInterface->GetDevice()->GetBus());
usbController->GetLowLatencyOptionsAndPhysicalMask(&usbOptions, &physicalMask);
usbOptions |= kIODirectionInOut;
mMemDesc = IOBufferMemoryDescriptor::inTaskWithPhysicalMask(kernel_task, usbOptions, memorySize, physicalMask);

This is what I have found in AppleUSBAudio and this is what I was missing, so thread priority was not my problem.

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References:
	>USB Audio driver and THREAD_TIME_CONSTRAINT_POLICY (From: Vyacheslav Matyushin <email@hidden>)

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