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From:   Nick Dyer <nick@shmanahar.org>
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
        Chris Healy <cphealy@gmail.com>,
        Nikita Yushchenko <nikita.yoush@cogentembedded.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Nick Dyer <nick.dyer@itdev.co.uk>
Subject: [PATCH v1 01/10] Input: atmel_mxt_ts - only use first T9 instance
Date:   Fri, 20 Jul 2018 22:51:13 +0100
Message-Id: <20180720215122.23558-1-nick@shmanahar.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Nick Dyer <nick.dyer@itdev.co.uk>

The driver only registers one input device, which uses the screen
parameters from the first T9 instance. The first T63 instance also uses
those parameters.

It is incorrect to send input reports from the second instances of these
objects if they are enabled: the input scaling will be wrong and the
positions will be mashed together.

This also causes problems on Android if the number of slots exceeds 32.

In the future, this could be handled by looking for enabled touch object
instances and creating an input device for each one.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Acked-by: Benson Leung <bleung@chromium.org>
Acked-by: Yufeng Shen <miletus@chromium.org>
---
 drivers/input/touchscreen/atmel_mxt_ts.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index 54fe190fd4bc..48c5ccab00a0 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -1658,10 +1658,11 @@ static int mxt_parse_object_table(struct mxt_data *data,
 			break;
 		case MXT_TOUCH_MULTI_T9:
 			data->multitouch = MXT_TOUCH_MULTI_T9;
+			/* Only handle messages from first T9 instance */
 			data->T9_reportid_min = min_id;
-			data->T9_reportid_max = max_id;
-			data->num_touchids = object->num_report_ids
-						* mxt_obj_instances(object);
+			data->T9_reportid_max = min_id +
+						object->num_report_ids - 1;
+			data->num_touchids = object->num_report_ids;
 			break;
 		case MXT_SPT_MESSAGECOUNT_T44:
 			data->T44_address = object->start_address;
-- 
2.17.1