Re: [PATCH v3] platform/x86: ideapad-laptop: do not poke keyboard controller

[Dmitry Torokhov]

Hi Rong,

On Sat, Oct 24, 2026 at 11:30:06PM +0800, Rong Zhang wrote:
> However, the methodology has been changed from hardware-based to
> software-based. Because of the fundamental change, it has the potential
> to break something if some users depends on the side-effect of toggling
> the aux port.
>
> While my device never needs the quirk, I can think of several useful
> side-effects:
>
> - pause the interrupt (and hence pause event handling) to save some
> energy
> - prevent the touchpad from waking up the platform
> - reset faulty touchpads
>
> By switching to the software-based methodology, all these capabilities
> have gone. Of course, relying on these side-effects is a misuse, but
> relying on the parameter itself without reporting it to the mailing list
> is also a misuse! More below.

This reminds me of https://xkcd.com/1172/ ("Workflow").

Also note that I8042_CMD_AUX_DISABLE / I8042_CMD_AUX_ENABLE only toggles
the AUX clock inhibit bit in the 8042 controller; it does not power down
or reset the touchpad (psmouse is unaware that ideapad-laptop poked the
controller behind its back, which is the whole problem), and i8042
already manages the AUX port and wakeup state across suspend and resume.

> A completely new behavior reusing an old knob is always prone to break
> *something* in a obscure way unless users are notified about the change.
> Breaking something with a visible warning [1] in kmsg is much better than
> potentially breaking something in radio silence. 
>
> We don't want to support poking i8042 anymore, so the use of
> 'ctrl_ps2_aux_port' is anyway becoming unsupported. The parameter was
> introduced only for debugging and is expected to be removed at any time.
> If users don't report their use of the parameter to the mailing list,
> they are already relying on a broken setup.
>
> By renaming it and breaking the unsupported setup loudly, we encourage
> users to report quirky devices, as well as getting rid of an outdated
> parameter name.
>
> [1]: ideapad_laptop: unknown parameter 'ctrl_ps2_aux_port' ignored

We already have DMI matching for this quirk (ctrl_ps2_aux_port_list[],
which has only ever contained the 2011 IdeaPad Z570 since commit
c69e7d843d2c added it in 2022), and the module parameter simply sets the
exact same priv->features.ctrl_ps2_aux_port flag as the DMI table.

Intentionally breaking the module parameter for anyone who might be
using it for its intended purpose (making the touchpad toggle hotkey
work on an older IdeaPad) just because of hypothetical spacebar-heating
workflows does not make sense to me.

Thanks.

-- 
Dmitry