On Tuesday 27 January 2009, Inaky Perez-Gonzalez wrote:
> > That sounds to me like "<this implementation> sucks".
>
> A lot. But is what the spec says :( And actually the code sucks
> even more. Trust me, I wrote it.
So to partition discussion a bit: for WUSB there's
an issue with block I/O performance, where three
layers don't mesh well:
(a) block, which mostly works in n*512 byte units;
(b) DMA, which mostly works in page (4K/8K) units;
(c) WUSB, which works in oddball sizes (3.5K, variable),
and *also* wants to splice in headers all over.
The WUSB spec imposes the oddball sizes; I presume
those headers are a hardware issue; and that conceptual
mess inevitably caused some code suckage too, which has
not yet been fixed. ;)
That's distinct from any issues USB 3.0 has, from
what stuck in my brain after a quick read: its 1KB
packets for bulk I/o work nicely with the block and
DMA layers.
Is that a good summary?
- Dave
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