From: Robin Murphy

Sent: 14 June 2019 16:06

...

Well, apart from the bit in DMA-API-HOWTO which has said this since
forever (well, before Git history, at least):

"The CPU virtual address and the DMA address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size.  This invariant
exists (for example) to guarantee that if you allocate a chunk
which is smaller than or equal to 64 kilobytes, the extent of the
buffer you receive will not cross a 64K boundary."

I knew it was somewhere :-)
Interestingly that also implies that the address returned for a size
of (say) 128 will also be page aligned.
In that case 128 byte alignment should probably be ok - but it is still
an API change that could have horrid consequences.

	David

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