i8042: Enable MUX on Sony VAIO VGN-CS series to fix touchpad

The touch sensor buttons on Sony VAIO VGN-CS series laptops (e.g. VGN-CS31S) are a separate PS/2 device. As the MUX is disabled for all VAIO machines by the nomux blacklist, the data from touch sensor buttons and touchpad are combined. The protocol used by the buttons is probably similar to the touchpad protocol (both are Synaptics) so both devices get enabled. The controller combines the data, creating a mess which results in random button clicks, touchpad stopping working and lost sync error messages:
psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 4 psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1 psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1 psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1 psmouse serio1: TouchPad at isa0060/serio1/input0 lost sync at byte 1 psmouse serio1: issuing reconnect request

Add a new i8042_dmi_forcemux_table whitelist with VGN-CS. With MUX enabled, touch sensor buttons are detected as separate device (and left disabled as there's currently no driver), fixing all touchpad problems.

---
 drivers/input/serio/i8042-x86ia64io.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

index 6cbbdc6e9687..56644c74828c 100644
@@ -530,6 +530,20 @@ static const struct dmi_system_id __initconst i8042_dmi_nomux_table[] = {
 	{ }
 };
 
+static const struct dmi_system_id __initconst i8042_dmi_forcemux_table[] = {
+	{
+		/*
+		 * Sony Vaio VGN-CS series require MUX or the touch sensor
+		 * buttons will disturb touchpad operation
+		 */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "VGN-CS"),
+		},
+	},
+	{ }
+};
+
 /*
  * On some Asus laptops, just running self tests cause problems.
  */

@@ -1163,6 +1177,9 @@ static int __init i8042_platform_init(void)
 	if (dmi_check_system(i8042_dmi_nomux_table))
 		i8042_nomux = true;
 
+	if (dmi_check_system(i8042_dmi_forcemux_table))
+		i8042_nomux = false;
+
 	if (dmi_check_system(i8042_dmi_notimeout_table))
 		i8042_notimeout = true;
 

Ondrej Zary

Hi,

[This is an automated email]

This commit has been processed by the -stable helper bot and determined to be a high probability candidate for -stable trees. (score: 24.5527)

The bot has tested the following trees: v4.16, v4.15.15, v4.14.32, v4.9.92, v4.4.126.

v4.16: Build OK!
v4.15.15: Build OK!
v4.14.32: Build OK!
v4.9.92: Build OK!
v4.4.126: Build OK!

Please let us know if you'd like to have this patch included in a stable tree.

--
Thanks,
Sasha

AFAIK, it was already included in various stable trees.

Ondrej Zary

Ah yes, indeed I see it proposed for various -stable trees.

I guess Greg is extra speedy these days :)