linux-kernel - [PATCH] driver:st1633: fixed multitouch incorrect coordinates

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Date:   Mon, 19 Aug 2019 15:38:34 +0530
From:   Dixit Parmar <dixitparmar19@...il.com>
To:     dmitry.torokhov@...il.com, rydberg@...math.org, martink@...teo.de,
        kuninori.morimoto.gx@...esas.com, robh@...nel.org,
        matthias.fend@...fvision.net, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Dixit Parmar <dixitparmar19@...il.com>
Subject: [PATCH] driver:st1633: fixed multitouch incorrect coordinates

From: Dixit Parmar <dixitparmar19@...il.com>

For Sitronix st1633 multi-touch controller driver the co-ordinates reported
for multiple fingers were wrong.

So the below mentioned bug was filed,
Bugzilla Bug ID: 204561

While reading co-ordinates from specified I2C registers, the X & Y
co-ordinates should be read from proper I2C address for particular finger as
specified in chip specific datasheet.

for single touch this logic is working fine. However, for multi-touch
scenario the logic of reading data from data buffer has issues.

This patch fixes the reading logic from data buffer.

Previous logic:
* Offset of X & Y Lower byte coordinate is increased by i no. only(by 1 Byte)
  for each finger.

New logic:
* The logic of reading X & Y Lower Byte coordinate needs to be increased
  by i+y for each time/finger.

Signed-off-by: Dixit Parmar <dixitparmar19@...il.com>
---
 drivers/input/touchscreen/st1232.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/input/touchscreen/st1232.c b/drivers/input/touchscreen/st1232.c
index 3492339..1139714 100644
--- a/drivers/input/touchscreen/st1232.c
+++ b/drivers/input/touchscreen/st1232.c
@@ -81,8 +81,10 @@ static int st1232_ts_read_data(struct st1232_ts_data *ts)
 	for (i = 0, y = 0; i < ts->chip_info->max_fingers; i++, y += 3) {
 		finger[i].is_valid = buf[i + y] >> 7;
 		if (finger[i].is_valid) {
-			finger[i].x = ((buf[i + y] & 0x0070) << 4) | buf[i + 1];
-			finger[i].y = ((buf[i + y] & 0x0007) << 8) | buf[i + 2];
+			finger[i].x = ((buf[i + y] & 0x0070) << 4) |
+					buf[i + y + 1];
+			finger[i].y = ((buf[i + y] & 0x0007) << 8) |
+					buf[i + y + 2];

 			/* st1232 includes a z-axis / touch strength */
 			if (ts->chip_info->have_z)
-- 
2.7.4