+The above events are not propagated by the driver, except for legacy
+compatibility purposes when hotkey_report_mode is set to 1.
+
+Compatibility notes:
+
+ibm-acpi and thinkpad-acpi 0.15 (mainline kernels before 2.6.23) never
+supported the input layer, and sent events over the procfs ACPI event
+interface.
+
+To avoid sending duplicate events over the input layer and the ACPI
+event interface, thinkpad-acpi 0.16 implements a module parameter
+(hotkey_report_mode), and also a sysfs device attribute with the same
+name.
+
+Make no mistake here: userspace is expected to switch to using the input
+layer interface of thinkpad-acpi, together with the ACPI netlink event
+interface in kernels 2.6.23 and later, or with the ACPI procfs event
+interface in kernels 2.6.22 and earlier.
+
+If no hotkey_report_mode module parameter is specified (or it is set to
+zero), the driver defaults to mode 1 (see below), and on kernels 2.6.22
+and earlier, also allows one to change the hotkey_report_mode through
+sysfs. In kernels 2.6.23 and later, where the netlink ACPI event
+interface is available, hotkey_report_mode cannot be changed through
+sysfs (it is read-only).
+
+If the hotkey_report_mode module parameter is set to 1 or 2, it cannot
+be changed later through sysfs (any writes will return -EPERM to signal
+that hotkey_report_mode was locked. On 2.6.23 and later, where
+hotkey_report_mode cannot be changed at all, writes will return -EACES).
+
+hotkey_report_mode set to 1 makes the driver export through the procfs
+ACPI event interface all hot key presses (which are *also* sent to the
+input layer). This is a legacy compatibility behaviour, and it is also
+the default mode of operation for the driver.
+
+hotkey_report_mode set to 2 makes the driver filter out the hot key
+presses from the procfs ACPI event interface, so these events will only
+be sent through the input layer. Userspace that has been updated to use
+the thinkpad-acpi input layer interface should set hotkey_report_mode to
+2.
+
+Hot key press events are never sent to the ACPI netlink event interface.
+Really up-to-date userspace under kernel 2.6.23 and later is to use the
+netlink interface and the input layer interface, and don't bother at all
+with hotkey_report_mode.
+