+ hotkey_source_mask:
+ bit mask that selects which hot keys will the driver
+ poll the NVRAM for. This is auto-detected by the driver
+ based on the capabilities reported by the ACPI firmware,
+ but it can be overridden at runtime.
+
+ Hot keys whose bits are set in both hotkey_source_mask
+ and also on hotkey_mask are polled for in NVRAM. Only a
+ few hot keys are available through CMOS NVRAM polling.
+
+ Warning: when in NVRAM mode, the volume up/down/mute
+ keys are synthesized according to changes in the mixer,
+ so you have to use volume up or volume down to unmute,
+ as per the ThinkPad volume mixer user interface. When
+ in ACPI event mode, volume up/down/mute are reported as
+ separate events, but this behaviour may be corrected in
+ future releases of this driver, in which case the
+ ThinkPad volume mixer user interface semanthics will be
+ enforced.
+
+ hotkey_poll_freq:
+ frequency in Hz for hot key polling. It must be between
+ 0 and 25 Hz. Polling is only carried out when strictly
+ needed.
+
+ Setting hotkey_poll_freq to zero disables polling, and
+ will cause hot key presses that require NVRAM polling
+ to never be reported.
+
+ Setting hotkey_poll_freq too low will cause repeated
+ pressings of the same hot key to be misreported as a
+ single key press, or to not even be detected at all.
+ The recommended polling frequency is 10Hz.
+