[PATCH] Input: sentelic - filtering out erratic movement

[Tai-hwa Liang <avatar@sentelic.com>]

It turns out that certain hardware sometime generates unexpected movement
during normal operation. This patch tries to filter out these erratic
movements which will cause unexpected cursor jumping to the top-left corner.

This patch also tries to fix jumpy(back and forth) scrolling in X11 by
accumulating both fingers' coordinates before reporting to the input-mt layer.

Bugzilla:	https://bugzilla.kernel.org/show_bug.cgi?id=43197
Reported-and-tested-by:	Aleksey Spiridonov <leks13@leks13.ru>
Tested-by:	Eddie Dunn <eddie.dunn@gmail.com>
Tested-by:	Olivier Goffart <olivier@woboq.com>
---
 drivers/input/mouse/sentelic.c |  114 ++++++++++++++++++++++++++--------------
 drivers/input/mouse/sentelic.h |   35 ++++++++++++
 2 files changed, 110 insertions(+), 39 deletions(-)

diff --git a/drivers/input/mouse/sentelic.c b/drivers/input/mouse/sentelic.c
index 3f5649f..995b395 100644
--- a/drivers/input/mouse/sentelic.c
+++ b/drivers/input/mouse/sentelic.c
@@ -707,7 +707,7 @@ static psmouse_ret_t fsp_process_byte(struct psmouse *psmouse)
 	struct fsp_data *ad = psmouse->private;
 	unsigned char *packet = psmouse->packet;
 	unsigned char button_status = 0, lscroll = 0, rscroll = 0;
-	unsigned short abs_x, abs_y, fgrs = 0;
+	unsigned short abs_x, abs_y, fgrs;
 	int rel_x, rel_y;
 
 	if (psmouse->pktcnt < 4)
@@ -721,64 +721,100 @@ static psmouse_ret_t fsp_process_byte(struct psmouse *psmouse)
 
 	switch (psmouse->packet[0] >> FSP_PKT_TYPE_SHIFT) {
 	case FSP_PKT_TYPE_ABS:
+		if ((packet[0] == 0x48 || packet[0] == 0x49) &&
+		    packet[1] == 0 && packet[2] == 0) {
+			/*
+			 * filtering out erratic movement which will cause
+			 * unexpected cursor jumping to the top-left corner
+			 */
+			packet[3] &= 0xf0;
+		}
 		abs_x = GET_ABS_X(packet);
 		abs_y = GET_ABS_Y(packet);
 
-		if (packet[0] & FSP_PB0_MFMC) {
+		if (!IS_MFMC(packet[0]) && (packet[0] & (FSP_PB0_LBTN |
+		    FSP_PB0_PHY_BTN)) == FSP_PB0_LBTN) {
 			/*
-			 * MFMC packet: assume that there are two fingers on
-			 * pad
+			 * On-pad click in SFAC mode should be handled
+			 * by userspace.  On-pad clicks in MFMC mode
+			 * are real clickpad clicks, and not ignored.
 			 */
-			fgrs = 2;
+			packet[0] &= ~FSP_PB0_LBTN;
+		}
+		if (abs_x == 0 || abs_y == 0) {
+			/*
+			 * workaround for buggy firmware which sends zero
+			 * coordinates even if there is finger on pad
+			 */
+			if (!IS_MFMC(packet[0])) {
+				/* don't report bad movement */
+				fgrs = 0;
+			} else {
+				/*
+				 * ignore finger up event for multiple finger
+				 * scenario
+				 */
+				return PSMOUSE_FULL_PACKET;
+			}
+		} else {
+			/* finger(s) down */
+			if (!IS_MFMC(packet[0])) {
+				/* SFAC, MFMC CPB packet */
+				fgrs = 1;
 
-			/* MFMC packet */
-			if (packet[0] & FSP_PB0_MFMC_FGR2) {
-				/* 2nd finger */
-				if (ad->last_mt_fgr == 2) {
+				/* no multi-finger information */
+				ad->last_mt_fgr = 0;
+
+				fsp_set_slot(dev, 0, true, abs_x, abs_y);
+				fsp_set_slot(dev, 1, false, 0, 0);
+			} else if (IS_MFMC_FGR1(packet[0])) {
+				/* MFMC 1st finger */
+				if (ad->last_mt_fgr == 1) {
 					/*
 					 * workaround for buggy firmware
 					 * which doesn't clear MFMC bit if
-					 * the 1st finger is up
+					 * the 2nd finger is up
 					 */
 					fgrs = 1;
-					fsp_set_slot(dev, 0, false, 0, 0);
-				}
-				ad->last_mt_fgr = 2;
+					fsp_set_slot(dev, 0, true,
+						     abs_x, abs_y);
+					fsp_set_slot(dev, 1, false, 0, 0);
+				} else {
+					fgrs = 2;
+					ad->last_mt_fgr = 1;
 
-				fsp_set_slot(dev, 1, fgrs == 2, abs_x, abs_y);
+					/*
+					 * accumulate the coordaintes and
+					 * proceed to the next run
+					 */
+					ad->mfmc_x1 = abs_x;
+					ad->mfmc_y1 = abs_y;
+				}
 			} else {
-				/* 1st finger */
-				if (ad->last_mt_fgr == 1) {
+				/* MFMC 2nd finger */
+				if (ad->last_mt_fgr == 2) {
 					/*
 					 * workaround for buggy firmware
 					 * which doesn't clear MFMC bit if
-					 * the 2nd finger is up
+					 * the 1st finger is up
 					 */
 					fgrs = 1;
-					fsp_set_slot(dev, 1, false, 0, 0);
+					fsp_set_slot(dev, 0, false, 0, 0);
+					fsp_set_slot(dev, 1, true,
+						     abs_x, abs_y);
+				} else {
+					fgrs = 2;
+					ad->last_mt_fgr = 2;
+
+					/* report both fingers' coordinate */
+					fsp_set_slot(dev, 1, true,
+						     abs_x, abs_y);
+					abs_x = ad->mfmc_x1;
+					abs_y = ad->mfmc_y1;
+					fsp_set_slot(dev, 0, true,
+						     abs_x, abs_y);
 				}
-				ad->last_mt_fgr = 1;
-				fsp_set_slot(dev, 0, fgrs != 0, abs_x, abs_y);
-			}
-		} else {
-			/* SFAC packet */
-			if ((packet[0] & (FSP_PB0_LBTN|FSP_PB0_PHY_BTN)) ==
-				FSP_PB0_LBTN) {
-				/* On-pad click in SFAC mode should be handled
-				 * by userspace.  On-pad clicks in MFMC mode
-				 * are real clickpad clicks, and not ignored.
-				 */
-				packet[0] &= ~FSP_PB0_LBTN;
 			}
-
-			/* no multi-finger information */
-			ad->last_mt_fgr = 0;
-
-			if (abs_x != 0 && abs_y != 0)
-				fgrs = 1;
-
-			fsp_set_slot(dev, 0, fgrs > 0, abs_x, abs_y);
-			fsp_set_slot(dev, 1, false, 0, 0);
 		}
 		if (fgrs > 0) {
 			input_report_abs(dev, ABS_X, abs_x);
diff --git a/drivers/input/mouse/sentelic.h b/drivers/input/mouse/sentelic.h
index aa697ec..0173fc5 100644
--- a/drivers/input/mouse/sentelic.h
+++ b/drivers/input/mouse/sentelic.h
@@ -90,6 +90,39 @@
 #define	FSP_PB0_MUST_SET	BIT(3)
 #define	FSP_PB0_PHY_BTN		BIT(4)
 #define	FSP_PB0_MFMC		BIT(5)
+/* packet type. See FSP_PKT_TYPE_XXX */
+#define	FSP_PB0_TYPE		(BIT(7) | BIT(6))
+#define	FSP_PB0_TYPE_REL	(0)
+#define	FSP_PB0_TYPE_ABS	BIT(6)
+#define	FSP_PB0_TYPE_NOTIFY	BIT(7)
+#define	FSP_PB0_TYPE_CUSTOM	(BIT(7) | BIT(6))
+
+/*
+ * physical clickpad button = MFMC packet without physical button.
+ */
+#define	IS_PHY_CPB(_pb0_)	\
+	(((_pb0_) & (FSP_PB0_TYPE | FSP_PB0_MFMC | FSP_PB0_PHY_BTN)) == \
+	(FSP_PB0_TYPE_ABS | FSP_PB0_MFMC))
+/*
+ * single-finger absolute coordinate
+ */
+#define	IS_SFAC(_pb0_)		\
+	(((_pb0_) & (FSP_PB0_TYPE | FSP_PB0_MFMC)) == FSP_PB0_TYPE_ABS)
+/*
+ * multi-finger multi-coordinate (physical clickpad button is excluded)
+ */
+#define	IS_MFMC(_pb0_)		\
+	(((_pb0_) & (FSP_PB0_TYPE | FSP_PB0_MFMC | FSP_PB0_PHY_BTN)) == \
+	(FSP_PB0_TYPE_ABS | FSP_PB0_MFMC | FSP_PB0_PHY_BTN))
+#define	IS_MFMC_FGR1(_pb0_)	\
+	(((_pb0_) & (FSP_PB0_TYPE | FSP_PB0_MFMC | FSP_PB0_PHY_BTN | \
+		FSP_PB0_MFMC_FGR2)) == (FSP_PB0_TYPE_ABS | \
+		FSP_PB0_MFMC | FSP_PB0_PHY_BTN))
+#define	IS_MFMC_FGR2(_pb0_)	\
+	(((_pb0_) & (FSP_PB0_TYPE | FSP_PB0_MFMC | FSP_PB0_PHY_BTN | \
+		FSP_PB0_MFMC_FGR2)) == (FSP_PB0_TYPE_ABS | \
+		FSP_PB0_MFMC | FSP_PB0_PHY_BTN | FSP_PB0_MFMC_FGR2))
+
 
 /* hardware revisions */
 #define	FSP_VER_STL3888_A4	(0xC1)
@@ -117,6 +150,8 @@ struct fsp_data {
 	unsigned char	last_reg;	/* Last register we requested read from */
 	unsigned char	last_val;
 	unsigned int	last_mt_fgr;	/* Last seen finger(multitouch) */
+	unsigned short	mfmc_x1;	/* X coordinate for the 1st finger */
+	unsigned short	mfmc_y1;	/* Y coordinate for the 1st finger */
 };
 
 #ifdef CONFIG_MOUSE_PS2_SENTELIC
-- 
1.7.9.5