What happens on your machine is that the touchpad is also in legacy
space (attaching as pms), and uses irq 12.

This is not handled by the pckbc@acpi attachment yet, because I was
expecting systems with PS/2-compatible touchpad to work with the legacy
pckbc@isa attachment, which registers the two interrupts (1 for
keyboard, 12 for mouse). The few systems tested where pckbc@acpi is an
improvement, have their touchpad behind i2c, as imt or ims devices).

I need to think a bit more on how to solve this - I would need the
pckbc@acpi driver to attach to two acpi nodes, which is not something
the BSD device model allows.