pci_set_dma_mask() on masks other than 0xffffffff (32-bit systems)

[Anthony Truong]

Hello,
Isn't this another reason for having the (controlled) bigphysarea into
the mainstream?
If our DMA devices are capable of handling only sub 32-bit DMA memory,
then they are limited to the first 16 MB set aside for GFP_DMA?  So if
we need more than 16 MB or if there is not enough left in this tiny
region, then we are finished :-(
Even when blessed with SG capable DMA engines, we have to make sure the
DMA processor capable of handling the worst-case scenario.  Like for a 4
MB buffer, it has to be able to fetch 1001 entry SG table.
Or maybe it's time to throw away all old and substandard HW.  Why do we
need to support them? :-(

Regards,
Anthony Dominic Truong.





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