[Qemu-devel] State of EHCI emulation for QEMU

[Jan Kiszka <jan.kiszka@web.de>]

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Hi all,

as you may know, there is an experimental git repository at

	git://git.kiszka.org/qemu.git ehci

that contains (primarily) David's work on an EHCI model for QEMU,
infrequently merges with latest git by me. As both David and I are short
on time ATM to drive this towards mainline integration, I'd like to
motivate some more contributions.

But first of all a summary of its state:
 - works OK for mass storage device pass-through
 - gives quite decent performance this way (I've once installed a
   complete Linux distro onto an USB disk this way)
 - reported to fail when passing through certain other host device types
   (e.g. the iPhone)
 - lacks integration with UHCI (currently, only EHCI is provided by
   that tree, breaking USB 1.1 devices)

David furthermore provided the following to-dos:
 - lacks periodic frames support
 - lacks isochronous traffic support
 - lacks split transactions support
 - NAK/reload support is kludgy at best
 - throttle interrupt rate based on OS settings

Regarding integration with UHCI: David once posted an RFC patch that
basically establishes the foundation for fixed device-to-controller
assignment [1][2]. Most real implementations do dynamic hand-over
between EHCI and UHCI, however, the spec allows static assignment as
well (which simplifies the implementation in QEMU).

Would be really nice to see this upstream rather sooner than later. I
think the major blocking point is just the companion controller
integration, then we would already be able to use it with USB disks/sticks.

So, if anyone is interested in picking up some open task, every
contribution is welcome!

Jan

[1] http://thread.gmane.org/gmane.comp.emulators.qemu/77130
[2] http://thread.gmane.org/gmane.comp.emulators.qemu/76072


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