Input: Add keycodes for electronic privacy screen on/off hotkeys

Input: Add keycodes for electronic privacy screen on/off hotkeys

Add keycodes for hotkeys toggling the electronic privacy screen found on
some laptops on/off.

There already is an API for eprivacy screens as kernel-mode-setting drm
connector object properties:
https://www.kernel.org/doc/html/latest/gpu/drm-kms.html#standard-connector-properties

this API also supports reporting when the eprivacy screen is turned on/off
by the embedded-controller (EC) in response to hotkey presses.

But on some laptops (e.g. the Dell Latitude 7300) the firmware does not
allow querying the presence nor the status of the eprivacy screen at boot.
This makes it impossible to implement the drm connector properties API
since drm objects do not allow adding new properties after creation and
the presence of the eprivacy cannot be detected at boot.

The first notice of the presence of an eprivacy screen on these laptops is
an EC generated (WMI) event when the eprivacy screen hotkeys are pressed.

In this case the new keycodes this change adds can be generated to notify
userspace of the eprivacy screen on/off hotkeys being pressed, so that
userspace can show the usual on-screen-display (OSD) notification for eprivacy
screen on/off to the user. This is similar to how e.g. touchpad on/off
keycodes are used to show the touchpad on/off OSD.

Signed-off-by: Hans de Goede <hansg@kernel.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://patch.msgid.link/20251020152331.52870-2-hansg@kernel.org
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>