Be more strict about linking to already-linked devices

The wcmLinkTouchAndPen function is responsible for associating the pen and
touch interfaces of a tablet. This association can be tripped up if multiple
devices with the same name are connected, so it includes code to prevent
linking to a device which already has been linked up. However, the condition
also checks that the device being considered is a tablet (i.e., stylus/eraser/
cursor; not pad/touch). This latter check seems nonsensical: it allows devices
to link to the first touch device they find, even if that device is already
linked up.

Disallowing multiple links to the same device prevents all three pen/touch/pad
devices from having wcmTouchDevice set up, however. Leaving the stricter
condition as-is could cause devices to be linked up incorrectly (e.g. if the
X server has {touch1, pen1, pad1, touch2, pen2, pad2}, then touch1 and pen1
would get linked, but pad1 and touch2 would get linked, and pen2/pad2 left
unlinked!). To prevent this, we disallow linking of pad interfaces, which
should not be a problem since the pad shouldn't need to use the wcmTouchDevice
variable.

Fixes: 8bb519ef2b ("Update wcmTouchDevice for touch interface")
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/src/wcmConfig.c b/src/wcmConfig.c
index 2402952..f85f1ca 100644
--- a/src/wcmConfig.c
+++ b/src/wcmConfig.c
@@ -492,6 +492,12 @@ static Bool wcmLinkTouchAndPen(InputInfoPtr pInfo)
 	WacomCommonPtr tmpcommon = NULL;
 	WacomDevicePtr tmppriv = NULL;
 
+	if (IsPad(priv))
+	{
+		DBG(4, priv, "No need to link up pad devices.\n");
+		return FALSE;
+	}
+
 	/* Lookup to find the associated pen and touch */
 	for (; device != NULL; device = device->next)
 	{
@@ -504,7 +510,7 @@ static Bool wcmLinkTouchAndPen(InputInfoPtr pInfo)
 		DBG(4, priv, "Considering link with %s...\n", tmppriv->name);
 
 		/* already linked devices */
-		if (tmpcommon->wcmTouchDevice && IsTablet(tmppriv))
+		if (tmpcommon->wcmTouchDevice)
 		{
 			DBG(4, priv, "A link is already in place. Ignoring.\n");
 			continue;