Some business laptops support HP SureView technology. Idea of this technology is to reduce viewing angle when user enable privacy mode.
More information about HP SureView: http://www1.hp.com/ctg/Manual/c05317278
It's seems like currently hp_wmi driver doesn't detected HP SureView button. When I press this button on HP Elite x2 1013 G3 keyboard driver report this error to dmesg:
[ 963.116683] hp_wmi: Unknown event_id - 20 - 0x1
Besides recognizing button it's also necessary to react to this button accordingly - trigger screen privacy mode.
As example there is HP Elite x2 1013 G3 manual: http://h10032.www1.hp.com/ctg/Manual/c06077534 (page 16; Action keys paragraph, first icon description).
Please let me know what additional information I can provide to help get this feature implemented in hp_wmi driver.