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DMA buffer
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DMA buffer

Hi,

I am trying to write driver for a PCI X card which is DMA capable.
What I want to do is allocate some memory (a buffer ring) which would
contain data to be DMAed by the device.
For this I am following these steps

1) my_buffer =
my_buffer_t*)IOMallocContiguous( (vm_size_t)sizeof(my_buffer_t), PAGE_SIZE,
&phyAddr)
2) Set the device's DMA buffer registers with phyAddr from above.
3) Start the DMA

Reading through the mailing list it seems that I need to get a
IOMemoryDescriptor object after step 2) and call its prepare method before
doing the DMA start.

The question is IOMallocContiguous will create a wired down memory in the
kernel then why to call IOMemoryDescriptor's prepare()?


Thanks,
Lalit.
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