With the INPUT_MT_TRACK flag set, the function input_mt_assign_slots()
can be used to match a new set of contacts against the currently used
slots. The algorithm used is based on Lagrange relaxation, and performs
very well in practice; slower than mtdev for a few corner cases, but
faster in most commonly occuring cases.
Tested-by: NBenjamin Tissoires <benjamin.tissoires@enac.fr>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

Most MT drivers perform the same actions on frame synchronization.
Some actions, like dropping unseen contacts, are also unnecessarily
complex. Collect common frame synchronization tasks in a new function,
input_mt_sync_frame(). Depending on the flags set, it drops unseen
contacts and performs pointer emulation.

With init flags and frame synchronization in place, most MT drivers
can be simplified. First out are the bcm5974 and hid-multitouch
drivers, following this patch.
Reviewed-and-tested-by: NBenjamin Tissoires <benjamin.tissoires@enac.fr>
Tested-by: NPing Cheng <pingc@wacom.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

Preparing to move more repeated code into the mt core, add a flags
argument to the input_mt_slots_init() function.
Reviewed-and-tested-by: NBenjamin Tissoires <benjamin.tissoires@enac.fr>
Tested-by: NPing Cheng <pingc@wacom.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

Move all MT-related things to a separate place. This saves some
bytes for non-mt input devices, and prepares for new MT features.
Reviewed-and-tested-by: NBenjamin Tissoires <benjamin.tissoires@enac.fr>
Tested-by: NPing Cheng <pingc@wacom.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

The current MT accessor function does not distinguish between the MT
values and the slot specification event. Add an accessor function for
the values only, and use it where appropriate.
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

Calculate a default based on the number of ABS axes, REL axes,
and MT slots for the device during input device registration.
Signed-off-by: NJeff Brown <jeffbrown@android.com>
Reviewed-by: NHenrik Rydberg <rydberg@euromail.se>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

The drivers using the type B protocol all report tracking information
the same way. The contact id is semantically equivalent to
ABS_MT_SLOT, and the handling of ABS_MT_TRACKING_ID only complicates
the driver. The situation can be improved upon by providing a common
pointer emulation code, thereby removing the need for the tracking id
in the driver.  This patch moves all tracking event handling over to
the input core, simplifying both the existing drivers and the ones
currently in preparation.
Acked-by: NPing Cheng <pingc@wacom.com>
Acked-by: NJiri Kosina <jkosina@suse.cz>
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

The MT slots devices all follow the same initialization pattern
of creating slots and hinting about buffer size. Let drivers call
an initialization function instead, and make sure it can be called
repeatedly without side effects.
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

In preparation for common code to handle a larger set of MT slots
devices, move the slots handling over to a separate file.
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>