Re: mouse problems in 2.4.2 -> lost byte

[Gunther.Mayer@t-online.de (Gunther Mayer)]

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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.

[-- Attachment #2: gm_psauxprint.c --]
[-- Type: application/octet-stream, Size: 771 bytes --]

// show effects of lost bytes on ps/2 mouse protocol 
#include <stdio.h>
#include <errno.h>
int main(void)
{ 
	FILE *f;
	int i=0,x,a,y, xo,yo,xs,ys,r,m,l,t,dx,dy;

	f=fopen("/dev/psaux","r");
	if(f==NULL) strerror(errno);

 //printf("Simulating 2 lost bytes\n");
 //a=fgetc(f); a=fgetc(f);

 printf("Simulating 1 lost byte\n");
 a=fgetc(f);
	while (1) {
		a=fgetc(f);
		x=fgetc(f);
		y=fgetc(f);
		i++;
		printf("%5d -- %02x %02x %02x",i,a,x,y);

		yo=a&0x80;
		xo=a&0x40;
		ys=a&0x20;
		xs=a&0x10;
		t=a&0x08;
		m=a&0x04;
		r=a&0x02;
		l=a&0x01;

		dx=x;
		dy=y;
		if(xs) dx=x-256;
		if(ys) dy=y-256;
		printf(" ---   %4d : %4d   Buttons=%s%s%s Overflow/errors:%s%s%s\n",
			dx,dy,m?"M":" ", r?"R":" ", l?"L":" ",
			xo?"X":" ", yo?"Y":" ", t?" ":"T");
	}
	return 0;
}