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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, KT Liao <kt.liao@emc.com.tw>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.4 025/190] Input: elantech - force relative mode on a certain module
Date:   Wed, 11 Apr 2018 20:34:31 +0200
Message-Id: <20180411183551.616035057@linuxfoundation.org>
In-Reply-To: <20180411183550.114495991@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/input/mouse/elantech.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -1715,6 +1715,17 @@ int elantech_init(struct psmouse *psmous
 			     etd->samples[0], etd->samples[1], etd->samples[2]);
 	}
 
+	if (etd->samples[1] == 0x74 && etd->hw_version == 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");