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Patch "Input: ALPS - fix multi-touch decoding on SS4 plus touchpads" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jan 20, 2018

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Stable branch Input drivers Alps ps/2 touchpad driver
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This is a note to let you know that I've just added the patch titled

Input: ALPS - fix multi-touch decoding on SS4 plus touchpads

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
input-alps-fix-multi-touch-decoding-on-ss4-plus-touchpads.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 4d94e776bd29670f01befa27e12df784fa05fa2e Mon Sep 17 00:00:00 2001

From: Nir Perry <[email protected]>
Date: Thu, 11 Jan 2018 23:43:26 -0800
Subject: Input: ALPS - fix multi-touch decoding on SS4 plus touchpads

From: Nir Perry <[email protected]>

commit 4d94e776bd29670f01befa27e12df784fa05fa2e upstream.

The fix for handling two-finger scroll (i4a646580f793 - "Input: ALPS - fix two-finger scroll breakage in right side on ALPS touchpad") introduced a minor "typo" that broke decoding of multi-touch events are decoded on some ALPS touchpads. For example, tapping with three-fingers can no longer be used to emulate middle-mouse-button (the kernel doesn't recognize this as the proper event, and doesn't report it correctly to userspace). This affects touchpads that use SS4 "plus" protocol variant, like those found on Dell E7270 & E7470 laptops (tested on E7270).

First, probably the code in alps_decode_ss4_v2() for case SS4_PACKET_ID_MULTI used inconsistent indices to "f->mt[]". You can see 0 & 1 are used for the "if" part but 2 & 3 are used for the "else" part.

Second, in the previous patch, new macros were introduced to decode X coordinates specific to the SS4 "plus" variant, but the macro to define the maximum X value wasn't changed accordingly. The macros to decode X values for "plus" variant are effectively shifted right by 1 bit, but the max wasn't shifted too. This causes the driver to incorrectly handle "no data" cases, which also interfered with how multi-touch was handled.

Fixes 4a646580f793 ("Input: ALPS - fix two-finger scroll breakage...")
Signed-off-by Nir Perry <[email protected]>
Reviewed-by Masaki Ota <[email protected]>
Signed-off-by Dmitry Torokhov <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/input/mouse/alps.c |   23 +++++++++++++----------
 drivers/input/mouse/alps.h |   10 ++++++----
 2 files changed, 19 insertions(+), 14 deletions(-)
drivers/input/mouse/alps.c +13 -10
@@ -1247,29 +1247,32 @@ static int alps_decode_ss4_v2(struct alp
 	case SS4_PACKET_ID_MULTI:
 		if (priv->flags & ALPS_BUTTONPAD) {
 			if (IS_SS4PLUS_DEV(priv->dev_id)) {
-				f->mt[0].x = SS4_PLUS_BTL_MF_X_V2(p, 0);
-				f->mt[1].x = SS4_PLUS_BTL_MF_X_V2(p, 1);
+				f->mt[2].x = SS4_PLUS_BTL_MF_X_V2(p, 0);
+				f->mt[3].x = SS4_PLUS_BTL_MF_X_V2(p, 1);
+				no_data_x = SS4_PLUS_MFPACKET_NO_AX_BL;
 			} else {
 				f->mt[2].x = SS4_BTL_MF_X_V2(p, 0);
 				f->mt[3].x = SS4_BTL_MF_X_V2(p, 1);
+				no_data_x = SS4_MFPACKET_NO_AX_BL;
 			}
+			no_data_y = SS4_MFPACKET_NO_AY_BL;
 
 			f->mt[2].y = SS4_BTL_MF_Y_V2(p, 0);
 			f->mt[3].y = SS4_BTL_MF_Y_V2(p, 1);
-			no_data_x = SS4_MFPACKET_NO_AX_BL;
-			no_data_y = SS4_MFPACKET_NO_AY_BL;
 		} else {
 			if (IS_SS4PLUS_DEV(priv->dev_id)) {
-				f->mt[0].x = SS4_PLUS_STD_MF_X_V2(p, 0);
-				f->mt[1].x = SS4_PLUS_STD_MF_X_V2(p, 1);
+				f->mt[2].x = SS4_PLUS_STD_MF_X_V2(p, 0);
+				f->mt[3].x = SS4_PLUS_STD_MF_X_V2(p, 1);
+				no_data_x = SS4_PLUS_MFPACKET_NO_AX;
 			} else {
-				f->mt[0].x = SS4_STD_MF_X_V2(p, 0);
-				f->mt[1].x = SS4_STD_MF_X_V2(p, 1);
+				f->mt[2].x = SS4_STD_MF_X_V2(p, 0);
+				f->mt[3].x = SS4_STD_MF_X_V2(p, 1);
+				no_data_x = SS4_MFPACKET_NO_AX;
 			}
+			no_data_y = SS4_MFPACKET_NO_AY;
+
 			f->mt[2].y = SS4_STD_MF_Y_V2(p, 0);
 			f->mt[3].y = SS4_STD_MF_Y_V2(p, 1);
-			no_data_x = SS4_MFPACKET_NO_AX;
-			no_data_y = SS4_MFPACKET_NO_AY;
 		}
 
 		f->first_mp = 0;
drivers/input/mouse/alps.h +6 -4
@@ -120,10 +120,12 @@ enum SS4_PACKET_ID {
 #define SS4_IS_5F_DETECTED(_b)	((_b[2] & 0x10) == 0x10)
 
 
-#define SS4_MFPACKET_NO_AX	8160	/* X-Coordinate value */
-#define SS4_MFPACKET_NO_AY	4080	/* Y-Coordinate value */
-#define SS4_MFPACKET_NO_AX_BL	8176	/* Buttonless X-Coordinate value */
-#define SS4_MFPACKET_NO_AY_BL	4088	/* Buttonless Y-Coordinate value */
+#define SS4_MFPACKET_NO_AX		8160	/* X-Coordinate value */
+#define SS4_MFPACKET_NO_AY		4080	/* Y-Coordinate value */
+#define SS4_MFPACKET_NO_AX_BL		8176	/* Buttonless X-Coord value */
+#define SS4_MFPACKET_NO_AY_BL		4088	/* Buttonless Y-Coord value */
+#define SS4_PLUS_MFPACKET_NO_AX		4080	/* SS4 PLUS, X */
+#define SS4_PLUS_MFPACKET_NO_AX_BL	4088	/* Buttonless SS4 PLUS, X */
 
 /*
  * enum V7_PACKET_ID - defines the packet type for V7

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/input-alps-fix-multi-touch-decoding-on-ss4-plus-touchpads.patch