Re: Kernel panic on Intel based Mac with more than 2GB of memory

Subject: Re: Kernel panic on Intel based Mac with more than 2GB of memory

From: Chris Sarcone <email@hidden>

Date: Thu, 12 Oct 2006 09:48:31 -0700

Delivered-to: email@hidden

Gerald --

This is weird. I've just converted a driver that was using IODMACommand
to use IOMemoryMap with MemMap->getPhysicalAddress() and
->getVirtualAddress.

NO! Don't do this. You're now causing every command that will be DMA'd to have a chunk of the kernel's Virtual Address space allocated and paying a huge performance penalty to go through VM for what should be just a DMA via the controller. Don't do this!

The original driver with IODMACommand worked OK on Intel systems
(MacBook Pro) up to and including 10.4.5, but NOT on 10.4.8. On a
PowerPC G5, the IODMACommand-ised driver worked OK up to 10.4.7 but
failed to load on 10.4.8.

You're probably compiling with the wrong headers. Make sure you have Xcode 2.4 and use the 10.4u SDK.

After converting the driver to use the MemMap scheme above, both Intel
and PowerPC versions worked fine on 10.4.5 and 10.4.8. I have yet to
test on 10.4.2.

And your performance probably dropped...

What's the official party line on this? Are we _definitely_ supposed to
use IODMACommand on 10.4.8?

Yes. IODMACommand is the supported interface moving forward. It should abstract everything that is required for DMA controllers. If you're missing something, let Apple know via bug reports.

NB. My driver does NOT use MemoryCursors any more.

Sorry to interrupt your discussion, but Chris' comment above had me
confused...

Please use IODMACommand, with the proper SDK/headers.

-- Chris

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References:
	>RE: Kernel panic on Intel based Mac with more than 2GB of memory (From: "Dave Canfield" <email@hidden>)
	>Re: Kernel panic on Intel based Mac with more than 2GB of memory (From: Chris Sarcone <email@hidden>)
	>Re: Kernel panic on Intel based Mac with more than 2GB of memory (From: Andrew Gallatin <email@hidden>)
	>Re: Kernel panic on Intel based Mac with more than 2GB of memory (From: Gerald Heinig <email@hidden>)