Comment 59 for bug 1722478

Here are the changes that went into Synaptics PS/2 driver:

git log --oneline v4.11.9..v4.12.7 -- drivers/input/mouse/synaptics.c
2fef826e45c6 Input: synaptics - tell users to report when they should be using rmi-smbus
f4101ff87daf Input: synaptics - warn the users when there is a better mode
f4947d79a708 Input: synaptics - keep PS/2 around when RMI4_SMB is not enabled
2755551188d2 Input: synaptics - clear device info before filling in
f6c4442bfa08 Input: synaptics - use u8 instead of unsigned char
212baf03a30a Input: synaptics - do not abuse -1 as return value
991d29fe02a7 Input: synaptics - use BIT() and GENMASK() macros
2c6ecbba90d4 Input: synaptics - add synaptics_query_int()
e839ffab0289 Input: synaptics - add support for Intertouch devices
6c53694fb222 Input: synaptics - split device info into a separate structure
996b9eedd061 Input: synaptics - do not mix logical and bitwise operations

The one I'd looked closer at is "991d29fe02a7 Input: synaptics - use BIT() and GENMASK() macros"> Can you try reverting them one by one and see which one is at fault?