[PATCH] Input: sentelic - filtering out erratic movement

[PATCH] Input: sentelic - filtering out erratic movement

[Tai-hwa Liang]

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

Re: [PATCH] Input: sentelic - filtering out erratic movement

[Tai-hwa Liang]

On Fri, 6 Jul 2012, Tai-hwa Liang wrote:
> 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>

   Signed-off-by:	Tai-hwa Liang <avatar@sentelic.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
>

Re: [PATCH] Input: sentelic - filtering out erratic movement

[Dmitry Torokhov]

Hi Tai-hwa,

On Fri, Jul 06, 2012 at 01:49:29PM +0800, Tai-hwa Liang wrote:
> 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;
> +		}

I am not sure if I understand this patch. According to the documentation
the above values for the packet[0] have the 'valid' bit 0 which means
that the touch data should be completely ignored instead of massaging
data like you seem to be doing.

Overall I wonder if you want to increase the size of the buffer to hold
both packets (for both fingers) and analyze both of them together...

It also appears that the patch does too many things at one and should be
split into several addressing individual issues.

Thanks.

-- 
Dmitry

Re: [PATCH] Input: sentelic - filtering out erratic movement

[Tai-hwa Liang]

On Wed, 25 Jul 2012, Dmitry Torokhov wrote:
> Hi Tai-hwa,
>
> On Fri, Jul 06, 2012 at 01:49:29PM +0800, Tai-hwa Liang wrote:
>> 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.
[...]
>> @@ -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;
>> +		}
>
> I am not sure if I understand this patch. According to the documentation
> the above values for the packet[0] have the 'valid' bit 0 which means
> that the touch data should be completely ignored instead of massaging
> data like you seem to be doing.

   I was thinking about keeping external button events for this case;
however, given that there is no input_report_key() for such events
(honestly, I don't even know any Real World setup for these),
a quick 'return PSMOUSE_FULL_PACKET;' should be enough.

> Overall I wonder if you want to increase the size of the buffer to hold
> both packets (for both fingers) and analyze both of them together...

   Would you please elaborate this a little more?  For now mfmc_[xy]1 are
used to store one finger such that driver can report both figners'
coordinates at once.  If you're referring to erratic movement packet like
the above, filtering one at a time should be enough since they can be
considered as sporadic noise input.

> It also appears that the patch does too many things at one and should be
> split into several addressing individual issues.

   Sure. I'll split jumping to top-left corner and jumpy X11 scrolling into
two different patches.

-- 
Thanks,

Tai-hwa Liang

[PATCH] Input: sentelic - filtering out erratic movement

[Tai-hwa Liang]

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.

Bugzilla:	https://bugzilla.kernel.org/show_bug.cgi?id=43197
Reported-by:	Aleksey Spiridonov <leks13@leks13.ru>
Tested-by:	Aleksey Spiridonov <leks13@leks13.ru>
Signed-off-by: Tai-hwa Liang <avatar@sentelic.com>
---
 drivers/input/mouse/sentelic.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/input/mouse/sentelic.c b/drivers/input/mouse/sentelic.c
index 3f5649f..48967a4 100644
--- a/drivers/input/mouse/sentelic.c
+++ b/drivers/input/mouse/sentelic.c
@@ -721,6 +721,14 @@ 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 top-left corner
+			 */
+			packet[3] &= 0xf0;
+		}
 		abs_x = GET_ABS_X(packet);
 		abs_y = GET_ABS_Y(packet);
 
-- 
1.7.10