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From: | Max Krasnyansky |
Subject: | [Qemu-devel] Re: USB-OHCI / UHCI: Isochronous transfer not working on Linux host |
Date: | Thu, 11 Dec 2008 10:46:43 -0800 |
User-agent: | Thunderbird 2.0.0.16 (X11/20080723) |
Sorry for delay in replying. (CCing Mark Burkley who recently posted EHCI patches) Thomas Bandelier wrote:
Most USB 2.0 devices should work just fine with the current UHCI code. Including isochronous transfers. While developing new UHCI implementation I was testing it with several 2.0 devices like USB storage devices and MS Webcam. Webcam uses isoc transfers and worked fairly well. However since UHCI does not do 2.0 rates USB bandwidth is much lower in the guest.Hi Arnon, Max, Pierre, Arnon, Thanks for your feedback on this point.As we need to manage several USB 2.0 devices in our environment, we are going to work on this aspect. We are very motivated to make it work.Do you (Max and/or Arnon) have any idea of what should be done / reworked in order to support USB 2.0 devices and especially isochronous transfers in QEMU?
We would prefer keeping OHCI implementation, but do you think we should switch to UHCI? Or maybe EHCI?Ideally we need to switch to EHCI in order to support high USB2.0 speeds. Not too long ago Mark posted a EHCI implementation (I have not had much luck with it and XP yet though).If we can keep OHCI, what should we begin to do in order to debug current QEMU OHCI implementation? Same question for the other controllers if we have to switch.
Otherwise if you're ok with lower BW then UHCI should work fine. Max
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