Quoting  from Jonathan Clarke in previous thread(2017/01/24):

"This division by 2 was added along with the touch width/height fields 6 years
ago so that those fields 'match the visual scale of the touch' for a specific
device (3M PCT)" "The scaling is also discarding information about touch size
(1 bit for each of width/height) which is useful for any application that wants
to know about it."

Jonathan mentioned just what I thought in a new project recently.  It dosen't
make sense to discard 1 bit width/height in general case according to the spec
in multi-touch-protocol.txt so I would like to make a slight change here.

A quirk MT_QUIRK_TOUCH_SIZE_SCALING was added to service devices like 3M PCT
with a special visual scale and the division by 2 only take effect with devices
like that.

[jkosina@suse.cz: reformat changelog]
Signed-off-by: HungNien Chen <hn.chen@weidahitech.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>