More robust resynchronization code, after an idea from

Hartwig Felger. When we realize we are out of sync, only throw away
one byte, not all bytes already read from the touchpad.

1 files changed, 41 insertions, 34 deletions

diff --git a/synaptics.c b/synaptics.c
index c8344fc..1e68622 100644
--- a/synaptics.c
+++ b/synaptics.c
@@ -1288,6 +1288,7 @@ QueryHardware (LocalDevicePtr local)
 	}
 	para->isSynaptics = priv->isSynaptics;
 
+	priv->protoBufTail = 0;
 	if(!priv->isSynaptics) {
 		xf86Msg(X_PROBED, "%s no synaptics touchpad, data piped to repeater fifo\n", local->name);
 		synaptics_reset(local->fd);
@@ -1523,12 +1524,43 @@ SynapticsParseRawPacket(LocalDevicePtr local, SynapticsPrivatePtr priv,
 	return Success;
 }
 
+/*
+ * Decide if the current packet stored in priv->protoBuf is valid.
+ */
+static Bool
+PacketOk(SynapticsPrivatePtr priv)
+{
+	unsigned char *buf = priv->protoBuf;
+	int newabs = SYN_MODEL_NEWABS(priv->model_id);
+
+	if (newabs ? ((buf[0] & 0xC8) != 0x80) : ((buf[0] & 0xC0) != 0xC0)) {
+		DBG(4, ErrorF("Synaptics driver lost sync at 1st byte\n"));
+		return FALSE;
+	}
+
+	if (!newabs && ((buf[1] & 0x60) != 0x00)) {
+		DBG(4, ErrorF("Synaptics driver lost sync at 2nd byte\n"));
+		return FALSE;
+	}
+
+	if ((newabs ? ((buf[3] & 0xc8) != 0xc0) : ((buf[3] & 0xc0) != 0x80))) {
+		DBG(4, ErrorF("Synaptics driver lost sync at 4th byte\n"));
+		return FALSE;
+	}
+
+	if (!newabs && ((buf[4] & 0x60) != 0x00)) {
+		DBG(4, ErrorF("Synaptics driver lost sync at 5th byte\n"));
+		return FALSE;
+	}
+
+	return TRUE;
+}
+
 static Bool
 SynapticsGetPacket(LocalDevicePtr local, SynapticsPrivatePtr priv)
 {
 	int count = 0;
 	int c;
-	int newabs = SYN_MODEL_NEWABS(priv->model_id);
 	unsigned char u;
 
 	while((c = XisbRead(priv->buffer)) >= 0) {
@@ -1564,41 +1596,16 @@ SynapticsGetPacket(LocalDevicePtr local, SynapticsPrivatePtr priv)
 
 		priv->protoBuf[priv->protoBufTail++] = u;
 
-		/* check first byte */
-		if(priv->protoBufTail == 1)
-		{
-			if (newabs ? ((u & 0xC8) != 0x80) : ((u & 0xC0) != 0xC0))
-			{
+		/* Check that we have a valid packet. If not, we are out of sync,
+		   so we throw away the first byte in the packet.*/
+		if (priv->protoBufTail >= 6) {
+			if (!PacketOk(priv)) {
+				int i;
 				priv->inSync = FALSE;
-				priv->protoBufTail = 0;
-				DBG(4, ErrorF("Synaptics driver lost sync at 1st byte\n"));
-				continue;
-			}
-		}
-		/* for old protocol check 2nd and 5th byte */
-		if (!newabs && ((priv->protoBufTail == 2) || (priv->protoBufTail == 5)) &&
-			((u & 0x60) != 0x00))
-		{
-			if (priv->protoBufTail == 2)
-			{
-				DBG(4, ErrorF("Synaptics driver lost sync at 2nd byte\n"));
-			}
-			else
-			{
-				DBG(4, ErrorF("Synaptics driver lost sync at 5th byte\n"));
+				for (i = 0; i < priv->protoBufTail - 1; i++)
+					priv->protoBuf[i] = priv->protoBuf[i + 1];
+				priv->protoBufTail--;
 			}
-			priv->inSync = FALSE;
-			priv->protoBufTail = 0;
-			continue;
-		}
-		/* check 4th byte */
-		if((priv->protoBufTail == 4) &&
-		   (newabs ? ((u & 0xc8) != 0xc0) : ((u & 0xc0) != 0x80)))
-		{
-			priv->inSync = FALSE;
-			priv->protoBufTail = 0;
-			DBG(4, ErrorF("Synaptics driver lost sync at 4th byte\n"));
-			continue;
 		}
 
 		if(priv->protoBufTail >= 6)