From f5d07b9e98022d50720e38aa936fc11c67868ece Mon Sep 17 00:00:00 2001
From: Aaron Ma <aaron.ma@canonical.com>
Date: Fri, 19 Jan 2018 09:43:39 -0800
Subject: [PATCH] Input: trackpoint - force 3 buttons if 0 button is reported
Git-commit: f5d07b9e98022d50720e38aa936fc11c67868ece
Patch-mainline: v4.15
References: bsc#1051510

Lenovo introduced trackpoint compatible sticks with minimum PS/2 commands.
They supposed to reply with 0x02, 0x03, or 0x04 in response to the
"Read Extended ID" command, so we would know not to try certain extended
commands. Unfortunately even some trackpoints reporting the original IBM
version (0x01 firmware 0x0e) now respond with incorrect data to the "Get
Extended Buttons" command:

 thinkpad_acpi: ThinkPad BIOS R0DET87W (1.87 ), EC unknown
 thinkpad_acpi: Lenovo ThinkPad E470, model 20H1004SGE

 psmouse serio2: trackpoint: IBM TrackPoint firmware: 0x0e, buttons: 0/0

Since there are no trackpoints without buttons, let's assume the trackpoint
has 3 buttons when we get 0 response to the extended buttons query.

Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196253
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/input/mouse/trackpoint.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/input/mouse/trackpoint.c
+++ b/drivers/input/mouse/trackpoint.c
@@ -383,6 +383,9 @@ int trackpoint_detect(struct psmouse *ps
 	if (trackpoint_read(ps2dev, TP_EXT_BTN, &button_info)) {
 		psmouse_warn(psmouse, "failed to get extended button data, assuming 3 buttons\n");
 		button_info = 0x33;
+	} else if (!button_info) {
+		psmouse_warn(psmouse, "got 0 in extended button data, assuming 3 buttons\n");
+		button_info = 0x33;
 	}
 
 	psmouse->private = kzalloc(sizeof(struct trackpoint_data), GFP_KERNEL);