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Re: [Qemu-devel] [PATCH] USB 2.0 EHCI emulation

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH] USB 2.0 EHCI emulation
Date: Tue, 08 Jan 2008 19:14:13 +0200
User-agent: Thunderbird (X11/20071115)

Paul Brook wrote:
On Tuesday 08 January 2008, Dor Laor wrote:
On Tue, 2008-01-08 at 01:30 +0000, Paul Brook wrote:
-The host kernel was configured with dynamic tick & hi-res timers, to
allow the desired timer resolution. USB 2.0 microframe is 125usec.
It still works even without accurate timing demands.
Only isochronous mode will have problems and it is not yet supported for

It could also cause problems for periodic interrupt transfers. It's not uncommon for linux hosts to have a minimum timer period of 10ms (100Hz). This means the periodic list will be traversed 80x slower than it should, so a typical for a mouse or tablet with a 10ms poll interval will only be polled every 800ms. 800ms lag on a mouse is unacceptable.

The existing USB hosts have similar issues. However the problem is an order of magnitude less severe, so isn't noticeable under normal circumstances.

Surely qemu should read the time and adjust? For example, a 1000Hz guest running on a 100Hz host will see a 10x slowdown in real time.

error compiling committee.c: too many arguments to function

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