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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     KT Liao <kt.liao@emc.com.tw>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.4 025/167] Input: elantech - force relative mode
 on a certain module
Thread-Topic: [PATCH AUTOSEL for 4.4 025/167] Input: elantech - force relative
 mode on a certain module
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Date:   Mon, 19 Mar 2018 16:05:52 +0000
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From: KT Liao <kt.liao@emc.com.tw>

[ Upstream commit d899520b0431e70279bfb5066ecb6dc91d0b7072 ]

One of Elan modules with sample version is 0x74 and hw_version is 0x03 has
a bug in absolute mode implementation, so let it run in default PS/2
relative mode.

Signed-off-by: KT Liao <kt.liao@emc.com.tw>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/input/mouse/elantech.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.=
c
index 51b96e9bf793..06ea28e5d7b4 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -1715,6 +1715,17 @@ int elantech_init(struct psmouse *psmouse)
 			     etd->samples[0], etd->samples[1], etd->samples[2]);
 	}
=20
+	if (etd->samples[1] =3D=3D 0x74 && etd->hw_version =3D=3D 0x03) {
+		/*
+		 * This module has a bug which makes absolute mode
+		 * unusable, so let's abort so we'll be using standard
+		 * PS/2 protocol.
+		 */
+		psmouse_info(psmouse,
+			     "absolute mode broken, forcing standard PS/2 protocol\n");
+		goto init_fail;
+	}
+
 	if (elantech_set_absolute_mode(psmouse)) {
 		psmouse_err(psmouse,
 			    "failed to put touchpad into absolute mode.\n");
--=20
2.14.1