Message-ID: <3AC0F4D5.9E45E60C@t-online.de>
Date: Tue, 27 Mar 2001 22:15:17 +0200
From: Gunther.Mayer@t-online.de (Gunther Mayer)
MIME-Version: 1.0
To: linas@linas.org
CC: linux-kernel@vger.kernel.org
Subject: Re: mouse problems in 2.4.2 -> lost byte
In-Reply-To: <20010325223358.71E5F1B7A4@backlot.linas.org>
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Sender: linux-kernel-owner@vger.kernel.org

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linas@linas.org wrote:

> 
> I am experiencing debilitating intermittent mouse problems & was about
...
> Symptoms:
> After a long time of flawless operation (ranging from nearly a week to
> as little as five minutes), the X11 pointer flies up to top-right corner,
                                                          ^^^^^^^^^^^^^^^^
> and mostly wants to stay there.  Moving the mouse causes a cascade of
> spurious button-press events get generated.

This is easily explained: some byte of the mouse protocol was lost.
(Some mouse protocols are even designed to allow
 easy resync/recovery by fixed bit patterns!)

Write an intelligent mouse driver for XFree86 to compensate for
lost bytes. 

Regards, Gunther

APPENDIX
========

Output ot litte test program:
> a.out
Simulating 1 lost byte
    1 -- ff 00 08 ---   -256 : -248   Buttons=MRL Overflow/errors:XY 
    2 -- 00 04 08 ---      4 :    8   Buttons=    Overflow/errors:  T
    3 -- 00 04 08 ---      4 :    8   Buttons=    Overflow/errors:  T
    4 -- 00 03 08 ---      3 :    8   Buttons=    Overflow/errors:  T
    5 -- 00 03 18 ---      3 :   24   Buttons=    Overflow/errors:  T
    6 -- ff 02 08 ---   -254 : -248   Buttons=MRL Overflow/errors:XY 
    7 -- 00 02 08 ---      2 :    8   Buttons=    Overflow/errors:  T
    8 -- 00 03 18 ---      3 :   24   Buttons=    Overflow/errors:  T
    9 -- ff 03 18 ---   -253 : -232   Buttons=MRL Overflow/errors:XY 
   10 -- ff 03 08 ---   -253 : -248   Buttons=MRL Overflow/errors:XY 
...

Probably XFree ignores data packets with XY overflow set. All other
packets move you to top-right corner.

Moving your mouse will quickly show button mania, as described by your post.
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