Ignore ABS_MISC as a source of device type information for AES pens

AES sensors "appear" to use protocol 5 since they send ABS_MISC events
which contain information about the tool type in use. The tool type
information sent by AES sensors does not contain stylus/eraser/puck
information, however, so we need to ignore it or else we may randomly
end up treating the pens as erasers if a certian bit is set.

Fixes: linuxwacom#74
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>

src/wcmUSB.c

@@ -1161,6 +1161,44 @@ static int usbFilterEvent(WacomCommonPtr common, struct input_event *event)
 	return 0;
 }
 
+/**
+ * Try to determine if a given tool ID belongs to an AES pen or not.
+ * Current definitions of the ID format define that bit 0 is a flag
+ * which indicates this. A few legacy pens have this bit set, however,
+ * making it hard to distinguish from this information alone. Ideally
+ * we would have a more robust mechanism that sets up an AES-specific
+ * protocol type at hotplug, but it seems I'm getting ahead of myself...
+ *
+ * @param id The tool id received from the kernel.
+ * @return 'true' if the tool uses AES, 'false' otherwise.
+ */
+static Bool toolIdIsAes(int id)
+{
+	if ((id & 0x01) == 0) {
+		return FALSE;
+	}
+
+	/* If an AES pen is ever released with one of these IDs, this
+	 * code will result in a false negative... *sigh*
+	 */
+	switch (id) {
+	        case 0x801: /* Intuos3 Inking pen */
+	        case 0x823: /* Intuos3 Grip Pen */
+	        case 0x813: /* Intuos3 Classic Pen */
+	        case 0x885: /* Intuos3 Marker Pen */
+	        case 0x007: /* Mouse 4D and 2D */
+	        case 0x017: /* Intuos3 2D Mouse */
+	        case 0x097: /* Intuos3 Lens cursor */
+	        case 0x82b: /* Intuos3 Grip Pen Eraser */
+	        case 0x81b: /* Intuos3 Classic Pen Eraser */
+	        case 0x91b: /* Intuos3 Airbrush Eraser */
+	        case 0x913: /* Intuos3 Airbrush */
+			return FALSE;
+	}
+
+	return TRUE;
+}
+
 #define ERASER_BIT      0x008
 #define PUCK_BITS	0xf00
 #define PUCK_EXCEPTION  0x806
@@ -1177,14 +1215,20 @@ static int usbIdToType(int id)
 	if (!id)
 		return 0;
 
-	/* The existing tool ids have the following patten: all pucks, except
-	 * one, have the third byte set to zero; all erasers have the fourth
-	 * bit set. The rest are styli.
-	 */
-	if (id & ERASER_BIT)
-		type = ERASER_ID;
-	else if (!(id & PUCK_BITS) || (id == PUCK_EXCEPTION))
-		type = CURSOR_ID;
+	if (toolIdIsAes(id)) {
+		/* Type information is not available from the ID for AES */
+		return 0;
+	}
+	else {
+		/* The existing EMR tool ids have the following patten: all
+		 * pucks, except one, have the third byte set to zero; all
+		 * erasers have the fourth bit set. The rest are styli.
+		 */
+		if (id & ERASER_BIT)
+			type = ERASER_ID;
+		else if (!(id & PUCK_BITS) || (id == PUCK_EXCEPTION))
+			type = CURSOR_ID;
+	}
 
 	return type;
 }