To make a long story short, mousedev.c does not properly implement the
EXPS/2 protocol, specificly dealing with the wheel.

The lower 8 bits of the 4th byte are supposed to be 0x1 or 0xf to
indicate movement of the first wheel, and 0x2 or 0xe for the second
wheel.

Attached is a patch to correct this.

This does not get my two wheel mouse working perfectly yet, sadly that
will take a bit of a hack, and I'm not sure where the best place to put
it is yet, but this gets it back to generating correct data.

Zephaniah E. Hull.
(Debian GPM maintainer.)

-- 
	1024D/E65A7801 Zephaniah E. Hull <warp@babylon.d2dc.net>
	   92ED 94E4 B1E6 3624 226D  5727 4453 008B E65A 7801
	    CCs of replies from mailing lists are requested.

  Yes, Java is so bulletproofed that to a C programmer it feels like
being in a straightjacket, but it's a really comfy and warm
straightjacket, and the world would be a safer place if everyone was
straightjacketed most of the time.        -- Overheard in the SDM.
diff -ur linux/drivers/input/mousedev.c linux.mine/drivers/input/mousedev.c
--- linux/drivers/input/mousedev.c	2001-09-30 15:26:05.000000000 -0400
+++ linux.mine/drivers/input/mousedev.c	2002-10-26 18:20:19.000000000 -0400
@@ -62,7 +62,7 @@
 	struct fasync_struct *fasync;
 	struct mousedev *mousedev;
 	struct mousedev_list *next;
-	int dx, dy, dz, oldx, oldy;
+	int dw, dx, dy, dz, oldx, oldy;
 	signed char ps2[6];
 	unsigned long buttons;
 	unsigned char ready, buffer, bufsiz;
@@ -117,6 +117,7 @@
 						case REL_X:	list->dx += value; break;
 						case REL_Y:	list->dy -= value; break;
 						case REL_WHEEL:	if (list->mode) list->dz -= value; break;
+						case REL_HWHEEL: if (list->mode == 2) list->dw -= value; break;
 					}
 					break;
 
@@ -260,9 +261,22 @@
 	list->bufsiz = off + 3;
 
 	if (list->mode == 2) {
-		list->ps2[off + 3] = (list->dz > 7 ? 7 : (list->dz < -7 ? -7 : list->dz));
-		list->dz -= list->ps2[off + 3];
-		list->ps2[off + 3] = (list->ps2[off + 3] & 0x0f) | ((list->buttons & 0x18) << 1);
+		if (!list->dz && !list->dw) {
+			list->ps2[off + 3] = 0;
+		} else if (list->dw > 0) {
+			list->ps2[off + 3] = 0x2;
+			list->dw--;
+		} else if (list->dw < 0) {
+			list->ps2[off + 3] = 0xe;
+			list->dw++;
+		} else if (list->dz > 0) {
+			list->ps2[off + 3] = 0x1;
+			list->dz--;
+		} else if (list->dz < 0) {
+			list->ps2[off + 3] = 0xf;
+			list->dz++;
+		}
+		list->ps2[off + 3] |= (list->buttons & 0x18) << 1;
 		list->bufsiz++;
 	}
 	
@@ -272,7 +286,7 @@
 		list->bufsiz++;
 	}
 
-	if (!list->dx && !list->dy && (!list->mode || !list->dz)) list->ready = 0;
+	if (!list->dx && !list->dy && (!list->mode || !list->dz) && ((list->mode != 2) || !list->dw)) list->ready = 0;
 	list->buffer = list->bufsiz;
 }
 [unhandled content-type:application/pgp-signature]