Input: i8042 - disable active multiplexing by default

Active multiplexing is a nice feature as it allows several pointing devices (such as touchpad and external mouse) use their native protocols at the same time. Unfortunately many manufacturers do not implement the feature properly even though they advertise it. The problematic implementations are never fixed, since Windows by default does not use this mode, and move from one BIOS/model of laptop to another. When active multiplexing is broken turning it on usually results in touchpad, keyboard, or both unresponsive.

With PS/2 usage on decline (most of PS/2 devices in use nowadays are internal laptop touchpads), I expect number of users who have laptops with working MUX implementation, docking stations with external PS/2 ports, and who are still using external PS/2 mice, to be rather small. Let's flip the default to be OFF and allow activating it through i8042.nomux=0 kernel option. We'll also keep DMI table where we can record known good models.

Quoted 8 lines · Dmitry Torokhov

Active multiplexing is a nice feature as it allows several pointing devices (such as touchpad and external mouse) use their native protocols at the same time. Unfortunately many manufacturers do not implement the feature properly even though they advertise it. The problematic implementations are never fixed, since Windows by default does not use this mode, and move from one BIOS/model of laptop to another. When active multiplexing is broken turning it on usually results in touchpad, keyboard, or both unresponsive.

Quoted 6 lines

With PS/2 usage on decline (most of PS/2 devices in use nowadays are internal laptop touchpads), I expect number of users who have laptops with working MUX implementation, docking stations with external PS/2 ports, and who are still using external PS/2 mice, to be rather small. Let's flip the default to be OFF and allow activating it through i8042.nomux=0 kernel option. We'll also keep DMI table where we can record known good models.

Being responsible for introducing a non-trivial portion of i8042_dmi_nomux_table[] entries:

Acked-by Jiri Kosina <[email protected]>

If nothing else, it'd make my life easier :)

[ ... snip ... ]

Quoted 8 lines

drivers/input/serio/i8042.c +0 -0

index f5a98af..9a97c2b 100644
@@ -39,7 +39,7 @@ static bool i8042_noaux;
 module_param_named(noaux, i8042_noaux, bool, 0);
 MODULE_PARM_DESC(noaux, "Do not probe or use AUX (mouse) port.");
 

drivers/input/serio/i8042.c static bool i8042_noaux; · line 42

Quoted 2 lines

drivers/input/serio/i8042.c +1 -1

-static bool i8042_nomux;
+static bool i8042_nomux = true;

Hmmm ... perhaps if we want to be really friendly, we should warn (and I definitely don't mean WARN(), but rather pr_info() or something) if we encounter that the cmdline contains 'i8042.nomux=1'.

/*
- * Some Fujitsu notebooks are having trouble with touchpads if
- * active multiplexing mode is activated. Luckily they don't have
- * external PS/2 ports so we can safely disable it.
- * ... apparently some Toshibas don't like MUX mode either and
- * die horrible death on reboot.
+ * Some laptops do increment active multiplexing mode correctly;
+ * unfortunately they are in minority.
*/

Quoted 9 lines · Dmitry Torokhov

/*
- * Some Fujitsu notebooks are having trouble with touchpads if
- * active multiplexing mode is activated. Luckily they don't have
- * external PS/2 ports so we can safely disable it.
- * ... apparently some Toshibas don't like MUX mode either and
- * die horrible death on reboot.
+ * Some laptops do increment active multiplexing mode correctly;
+ * unfortunately they are in minority.
*/

s/increment/implement/ ?

Quoted 12 lines · Dave Jones

Quoted 9 lines · Dmitry Torokhov

/*
- * Some Fujitsu notebooks are having trouble with touchpads if
- * active multiplexing mode is activated. Luckily they don't have
- * external PS/2 ports so we can safely disable it.
- * ... apparently some Toshibas don't like MUX mode either and
- * die horrible death on reboot.
+ * Some laptops do increment active multiplexing mode correctly;
+ * unfortunately they are in minority.
*/

Quoted 1 line

s/increment/implement/ ?

Thanks Dave, I'll fix it up.

Active multiplexing is a nice feature as it allows several pointing devices (such as touchpad and external mouse) use their native protocols at the same time. Unfortunately many manufacturers do not implement the feature properly even though they advertise it. The problematic implementations are never fixed, since Windows by default does not use this mode, and move from one BIOS/model of laptop to another. When active multiplexing is broken turning it on usually results in touchpad, keyboard, or both unresponsive.

With PS/2 usage on decline (most of PS/2 devices in use nowadays are internal laptop touchpads), I expect number of users who have laptops with working MUX implementation, docking stations with external PS/2 ports, and who are still using external PS/2 mice, to be rather small. Let's flip the default to be OFF and allow activating it through i8042.nomux=0 kernel option. We'll also keep DMI table where we can record known good models.

Signed-off-by Dmitry Torokhov <[email protected]>

Quoted 15 lines · Dmitry Torokhov

Active multiplexing is a nice feature as it allows several pointing devices (such as touchpad and external mouse) use their native protocols at the same time. Unfortunately many manufacturers do not implement the feature properly even though they advertise it. The problematic implementations are never fixed, since Windows by default does not use this mode, and move from one BIOS/model of laptop to another. When active multiplexing is broken turning it on usually results in touchpad, keyboard, or both unresponsive.

With PS/2 usage on decline (most of PS/2 devices in use nowadays are internal laptop touchpads), I expect number of users who have laptops with working MUX implementation, docking stations with external PS/2 ports, and who are still using external PS/2 mice, to be rather small. Let's flip the default to be OFF and allow activating it through i8042.nomux=0 kernel option. We'll also keep DMI table where we can record known good models.

Quoted 1 line

Signed-off-by Dmitry Torokhov <[email protected]>

Could we keep the old default / blacklist for the old laptops? We did something like that for ACPI, based on year of the bios.

Old laptops are not being made any more, so blacklist will not grow too fast...