On Fri, Oct 12, 2018 at 04:24:08PM +0200, Benjamin Tissoires wrote:

Since v4.18, we unconditionally switch the I2C capable touchpads over I2C.
In the model I had (a pre-prod t480s I guess), the touchpad was behaving
fine.
However, it occurs that later production models don't expose the clickpad
information from I2C. The Windows driver gets all the information from PS/2
so we should do the same.

The situation is even worse for the P52. Once of the query parameter function
fails, which means the touchpad doesn't even probe. This effectively kills
the touchpad, which is less than ideal.

Dmitry, I am not sure if we should take those for stable in v4.18+.
I'd like to, but given the series is 5 patches, I don't know if this
will be acceptable.
We could revert in stable df077237cf55928f5 but that would mean
distributions will have to revert the revert if they want to provide
the I2C behavior.

So, regarding stable: your call :)

Heh ;) I think we have to fix it at least in 4.19 stable train. How
about we merge it normally into 4.20, and let it cook there for a while.
If there is no issues, then we can send it to 4.19 stable manually. How
does this sound?

Thanks.

-- 
Dmitry