From 13b35027202496be168b3c345cd6fc65055f9604 Mon Sep 17 00:00:00 2001
From: Peter Hutterer <peter.hutterer@who-t.net>
Date: Wed, 24 Oct 2018 10:35:17 +1000
Subject: [PATCH 4/4] Remember the event types we receive and skip events with
 no data

On RHEL7.x kernels we get event frames with merely MSC_SERIAL -1 for some
devices on proximity in. This is caused by the accelerometer data that is
otherwise suppressed by those kernels.

E: 123.456 0000 0000 0000       # ------------ SYN_REPORT (0) ----------
E: 123.456 0004 0000 -001       # EV_MSC / MSC_SERIAL           -1

For a MSC_SERIAL -1 we default to the PAD_ID (0x10), despite the events
happening on the Pen device node. This triggers an error message during EV_SYN
processing:

   (EE) usbDispatchEvents: Device Type mismatch - 16 -> 0. This is a BUG.

Once we receive the BTN_TOOL_PEN when the actual pen comes into proximity, the
error message goes away because our tool type matches with what we expect.

Fix this issue by remembering which event types we received in the current
frame. If all we got was EV_MSC, skip the event dispatch - we don't have any
data to process anyway.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
(cherry picked from commit 84400df38f0f9abe664de26a8d3747b10f3a05e5)
---
 src/wcmUSB.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/wcmUSB.c b/src/wcmUSB.c
index cf89ff8..2bb6b78 100644
--- a/src/wcmUSB.c
+++ b/src/wcmUSB.c
@@ -38,6 +38,7 @@ typedef struct {
 	int wcmMTChannel;
 	int wcmEventCnt;
 	struct input_event wcmEvents[MAX_USB_EVENTS];
+	uint32_t wcmEventFlags;      /* event types received in this frame */
 	int nbuttons;                /* total number of buttons */
 	int npadkeys;                /* number of pad keys in the above array */
 	int padkey_code[WCM_MAX_BUTTONS];/* hardware codes for buttons */
@@ -973,6 +974,13 @@ static int usbChooseChannel(WacomCommonPtr common, int device_type, unsigned int
 	return channel;
 }
 
+static inline void
+usbResetEventCounter(wcmUSBData *private)
+{
+	private->wcmEventCnt = 0;
+	private->wcmEventFlags = 0;
+}
+
 static void usbParseEvent(InputInfoPtr pInfo,
 	const struct input_event* event)
 {
@@ -989,12 +997,13 @@ static void usbParseEvent(InputInfoPtr pInfo,
 	{
 		LogMessageVerbSigSafe(X_ERROR, 0, "%s: usbParse: Exceeded event queue (%d) \n",
 				      pInfo->name, private->wcmEventCnt);
-		private->wcmEventCnt = 0;
+		usbResetEventCounter(private);
 		return;
 	}
 
 	/* save it for later */
 	private->wcmEvents[private->wcmEventCnt++] = *event;
+	private->wcmEventFlags |= 1 << event->type;
 
 	switch (event->type)
 	{
@@ -1032,7 +1041,7 @@ static void usbParseMscEvent(InputInfoPtr pInfo,
 		LogMessageVerbSigSafe(X_ERROR, 0,
 				      "%s: usbParse: Ignoring event from invalid serial 0\n",
 				      pInfo->name);
-		private->wcmEventCnt = 0;
+		usbResetEventCounter(private);
 	}
 }
 
@@ -1048,6 +1057,7 @@ static void usbParseSynEvent(InputInfoPtr pInfo,
 	WacomDevicePtr priv = (WacomDevicePtr)pInfo->private;
 	WacomCommonPtr common = priv->common;
 	wcmUSBData* private = common->private;
+	const uint32_t significant_event_types = ~(1 << EV_SYN | 1 << EV_MSC);
 
 	if (event->code != SYN_REPORT)
 		return;
@@ -1060,9 +1070,11 @@ static void usbParseSynEvent(InputInfoPtr pInfo,
 		goto skipEvent;
 	}
 
-	/* ignore sync windows that contain no data */
-	if (private->wcmEventCnt == 1 &&
-	    private->wcmEvents->type == EV_SYN) {
+
+	/* If all we get in an event frame is EV_SYN/EV_MSC, we don't have
+	 * real data to process. */
+	if ((private->wcmEventFlags & significant_event_types) == 0)
+	{
 		DBG(6, common, "no real events received\n");
 		goto skipEvent;
 	}
@@ -1071,7 +1083,7 @@ static void usbParseSynEvent(InputInfoPtr pInfo,
 	usbDispatchEvents(pInfo);
 
 skipEvent:
-	private->wcmEventCnt = 0;
+	usbResetEventCounter(private);
 }
 
 static int usbFilterEvent(WacomCommonPtr common, struct input_event *event)
-- 
2.19.2