If the tablet is locked, it should be - "1" is written to /sys/devices/platform/omap2_mcspi.1/spi1.0/disable_tp by MCE/SystemUI AFAIK. My understanding of the kernel is rudimentary but if the sysfs interface is anything like the procfs one, isn't a function (via a pointer) invoked when a file is written/to be written to, so even if it's not "disabled" (i.e. events are still picked up but not acted upon), you can still get notification and stop the polling accordingly?