Re: Synaptics and TrackPoint problems in 2.6.12

[Sergey Vlasov <vsu@altlinux.ru>]

On Tue, 19 Jul 2005 23:40:18 -0400 Stephen Evanchik wrote:

> I have been receiving a lot of complaints that TrackPoints on
> Synaptics pass-thru ports stopped working with 2.6.12. I retested
> 2.6.9 and 2.6.11-rc3 successfully, I believe 2.6.11.7 may also work
> but that is unconfirmed at this point.
> 
> The behavior is always the same .. after sending the read secondary ID
> command, the TrackPoint seems to be disabled from that point forward.
> 
> Any ideas?

Looks like this problem was introduced by the change from PSMOUSE_PS2 to
PSMOUSE_TRACKPOINT in the TrackPoint support patch.  The Synaptics
driver needs to know whether the device on the pass-thru port is using
3-byte or 4-byte packets; however, instead of checking child->pktsize,
it checks child->type >= PSMOUSE_GENPS - and this check is now giving a
wrong result.  Therefore the Synaptics driver configures the pass-thru
port for 4-byte packets, and all 3-byte packets from TrackPoint seem to
be thrown away.

The patch below is reported to fix the problem - now the 4-byte mode is
used only if child->pktsize == 4.  Another option is to change the
PSMOUSE_TRACKPOINT value so that it is less than PSMOUSE_GENPS, however,
I think that checking child->pktsize is more correct in this case.

In theory, someone could attach a device which uses 6-byte packets to
the Synaptics pass-thru port; I'm not sure what would happen in this
case, but with Synaptics confugured for 3-byte packets (as the patch
below will do) this configuration even has a chance of working.

---
Subject: [PATCH] Fix pass-thru port configuration in the Synaptics driver

The Synaptics driver uses child->type to select either 3-byte or 4-byte
packet size for the pass-thru port; this gives wrong results at least
for PSMOUSE_TRACKPOINT.  Change the check to use child->pktsize instead.

Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>

--- linux-2.6.12/drivers/input/mouse/synaptics.c.alt-synaptics-with-trackpoint	2005-06-17 23:48:29 +0400
+++ linux-2.6.12/drivers/input/mouse/synaptics.c	2005-07-09 21:09:01 +0400
@@ -219,7 +219,7 @@ static void synaptics_pass_pt_packet(str
 		serio_interrupt(ptport, packet[1], 0, NULL);
 		serio_interrupt(ptport, packet[4], 0, NULL);
 		serio_interrupt(ptport, packet[5], 0, NULL);
-		if (child->type >= PSMOUSE_GENPS)
+		if (child->pktsize == 4)
 			serio_interrupt(ptport, packet[2], 0, NULL);
 	} else
 		serio_interrupt(ptport, packet[1], 0, NULL);
@@ -233,7 +233,7 @@ static void synaptics_pt_activate(struct
 
 	/* adjust the touchpad to child's choice of protocol */
 	if (child) {
-		if (child->type >= PSMOUSE_GENPS)
+		if (child->pktsize == 4)
 			priv->mode |= SYN_BIT_FOUR_BYTE_CLIENT;
 		else
 			priv->mode &= ~SYN_BIT_FOUR_BYTE_CLIENT;

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