Hi Aaron,

On Fri, Jan 05, 2018 at 09:29:26PM +0800, Aaron Ma wrote:

Hi Dmitry:

Got the official info from Lenovo:
Lenovo introduced new TrackPoint compatible sticks ( ELAN/Alps/NXP
sticks) from 2016.
These new devices only support the minimum commands described in the
spec, which has been used in the current Windows driver.

What is the exact list of the commands supported by each variant?

Legacy TrackPoint: 0101 – 0E01
ALPS: 0102 – FF02
ELAN:0103 – FF03
NXP: 0104 – FF04

2.4.18 READ SECONDARY ID (x"E1")
This command will read the secondary device ID of the pointing device (2
bytes).  The least significant byte is sent first.  For the first byte,
the legacy TrackPoint controller from IBM will always return x"01", the
pointing stick from ALPS will always return x"02", the pointing stick
from Elan will always return x"03”, and the pointing stick from NXP will
always return 0x”04".  And a second byte which denotes a specific set of
functional specifications.  Differing ROM versions are used to denote
changes within a given functional set.

Can you/Lenovo share the updated spec?

The new devices (include Legacy ID:01) will not support the sysfs like
speed.

So it is not right to revert the commit, it is about to add another 0x04
ID in it.

Old sysfs could be stayed for old legacy device ID:01 or removed.

No, because there are devices that have trackpoints properly
implementing the protocol, before Lenovo started their "innovation".

Do we have any way to distinguish between properly implemented
trackpoints and Lenovo "improved" ones? I played with gen3 Carbon, and
while it does not error out on "speed" attribute, unlike gen5, it still
has no visible effects. Additionally, the "press to select"
functionality seems to be disabled, and trying to enable it via sysfs
results in register content being reverted to the original "disabled"
setting in a second or two. Setting to swap X and Y axes does not work
either, not sure about other bits of that control register.
"sensitivity" does work though, again unlike my gen5.

Thanks.

-- 
Dmitry