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Date: Wed, 17 Oct 2012 12:58:19 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] udev 42-qemu-usb.rules considered harmful?
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To: Michael Tokarev <mjt@tls.msk.ru>
Cc: qemu-devel <qemu-devel@nongnu.org>

  Hi,

> But the mouse is jumpy anyway.  I guess one can get used to this
> behavour, given the tradeoff and that the behavour is not VERY annoying --
> it is annoying, but just for a "bit", it feels like old mechanical
> mouse with bad sensor or dirty ball when you can move the mouse but
> cursor sometimes stays in place and sometimes moves, depending on
> the surface and direction of the move... ;)

How long are the delays for you?

> What happens when the (device, bus) is suspended?  Does host still
> sends interrupts periodically (but with much lower frequency)?  Or
> is it the bus/hub/device which should signal attention at some point?

UHCI raises an IRQ, guest restarts USB bus in response.  Which takes a
bit of time, so the first mouse event of an idle tablet takes a little
bit longer.  As far I know linux schedules the first poll a bit in the
future, so this could be where the delay comes from.

Do you also see delays with xhci? (-device nec-pci-xhci -device
usb-tablet) ?

cheers,
  Gerd