I think this would be less controversial if the run-time default were
to disable the feature.

Yes, that's the common sensible path to new little-tested features.
As you say, it may become enabled by default over time.

Then, I think it would be good to have a specific sub-structure for
this stuff. It would allow this:

  +       psmouse->err_log_base = 0;
  +       psmouse->interval_base = 0;
  +       psmouse->hotio_log_base = 0;
  +       psmouse->err_log_counter = 0;
  +       psmouse->interval_pkts = 0;
  +       psmouse->hotio_log_counter = 0;

to be replaced with a memset. I also think it would make it clearer
what these are:

  +       unsigned long interval_base;
  +       unsigned long interval_pkts;
  +       unsigned long hotio_log_base;
  +       unsigned long hotio_log_counter;
  +       unsigned long err_log_base;
  +       unsigned long err_log_counter;

to the casual reader.

This is only a suggestion, though.

thanks
/alessandro