Input: trackpoint - force 3 buttons if 0 button is reported

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>

diff --git a/drivers/input/mouse/trackpoint.c b/drivers/input/mouse/trackpoint.c
index 0871010f18d5f449e6440a5e41f71d24b8aecfd2..92a8898682a6d8460a4e23c081e3395cb59e08c8 100644 (file)
--- a/drivers/input/mouse/trackpoint.c
+++ b/drivers/input/mouse/trackpoint.c
@@ -383,6 +383,9 @@ int trackpoint_detect(struct psmouse *psmouse, bool set_properties)
        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);