[RFC libinput 0/9] touchpad: force resolutions for all touchpads

Bill Spitzak spitzak at gmail.com
Wed Jul 1 13:22:45 PDT 2015

On Tue, Jun 30, 2015 at 11:08 PM, Peter Hutterer <peter.hutterer at who-t.net>

> Not all touchpads provide x/y axis resolution. some of them (apple
> touchpads) we fix up in the systemd hwdb but others are harder to detect or
> fix in a generic manner. so we set a fake resolution (1 unit/mm), but
> that's
> just to avoid divide-by-zero.
> the touchpad code handles physical distances where possible but always has
> an escape path to handle the resolution-less touchpads, most of that by
> some
> magic numbers or percentages but those may or may not be correct.
> especially
> on the touchpads we don't have available for testing we have no idea how
> close the behaviour is to the intended one.
> this patchset does away with the fake resolution handling. a udev callout
> checks for the firmware version and assigns a tag based on that, the hwdb
> we
> ship then assigns size hints for the device. anything that doesn't get a
> size hint is simply set to a default size.
> this may make some touchpads worse in the short term, but long term we
> should be able to narrow down the various sizes and provide hwdb entries
> for
> them - and get the same behaviour across devices.
> Note that the hwdb entries are just approximates so far, the ALPS fw
> version
> 8 is a measurement of such a device, everything else is just assumption or
> blind guesses. I'll try to collect some real-world sizes before pushing
> this if we're happy with this approach.
> 1/9 and 2/9 are independent and can go in regardless.

Looks correct to me.

I hope my attempt to do this was helpful, but this approach where it can
get the size from the database is much better.
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