linux-kernel - [PATCH] Input: elantech

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Date:   Thu, 27 Feb 2020 11:59:16 +0000
From:   Bernd Edlinger <bernd.edlinger@...mail.de>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Enrico Weigelt <info@...ux.net>,
        Allison Randal <allison@...utok.net>,
        Aaron Ma <aaron.ma@...onical.com>
Subject: [PATCH] Input: elantech - fix x_max/y_max values

Since 37548659bb2 moved the querying of the x_max/y_max
values from elantech_set_input_params to elantech_query_info,
the returned x_max/y_max values are different than before,
at least for some firmware versions.

The reason is likely that this is now done before
elantech_set_absolute_mode does run.  So it may happen that
the returned values are exactly half of what they used to be,
which makes input_report_abs in PS/2 mode report ABS_X values which
exceed the x_max value, which is very annoying since the mouse stops
to move then, and ABS_Y value become negative, which is benign.

This was observed with a MSI GX70 laptop:

elantech: assuming hardware version 3 (with firmware version 0x250f01)
elantech: Synaptics capabilities query result 0x18, 0x17, 0x0b.
elantech: Elan sample query result 05, 0e, 00
input: ETPS/2 Elantech Touchpad as /devices/platform/i8042/serio...

Correct this by doubling the returned x_max and y_max
value for this specific firmware version.

Fixes: 37548659bb2 ("Input: elantech - query the min/max
information beforehand too")

Signed-off-by: Bernd Edlinger <bernd.edlinger@...mail.de>
---
 drivers/input/mouse/elantech.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index 2d8434b..3399db8 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -1720,6 +1720,10 @@ static int elantech_query_info(struct psmouse *psmouse,

 		info->x_max = (0x0f & param[0]) << 8 | param[1];
 		info->y_max = (0xf0 & param[0]) << 4 | param[2];
+		if (info->fw_version == 0x250f01) {
+			info->x_max <<= 1;
+			info->y_max <<= 1;
+		}
 		break;

 	case 4:
-- 
1.9.1