treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 55

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version of 2 of the license or
at your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 4 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520071858.207758043@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Input: wacom_serial4 - add support for Wacom ArtPad II tablet

Tablet initially begins communicating at 9600 baud, so this command
should be used to connect to the device:

$ inputattach --daemon --baud 9600 --wacom_iv /dev/ttyS0

https://github.com/linuxwacom/xf86-input-wacom/issues/40

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: wacom_serial4 - constify serio_device_id

serio_device_id are not supposed to change at runtime. All functions
working with serio_device_id provided by <linux/serio.h> work with
const serio_device_id. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: wacom_serial4 - prepare for wacom USB moving to HID

wacom_wac.h will be moving to drivers/hid. Since we only need 3 definitions
from it let's simply copy them over.

Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Input: add support for Wacom protocol 4 serial tablets

Recent version of xf86-input-wacom no longer support directly accessing
serial tablets. Instead xf86-input-wacom now expects all wacom tablets to
be driven by the kernel and to show up as evdev devices.

This has caused old serial Wacom tablets to stop working for people who still
have such tablets. Julian Squires has written a serio input driver to fix this:
https://github.com/tokenrove/wacom-serial-iv

This is a cleaned up version of this driver with improved Graphire support
(I own an old Graphire myself).

Signed-off-by: Julian Squires <julian@cipht.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>