Le 16 août 10 à 17:30, Henrik Rydberg a écrit :
Stéphane, Jiri,
Regarding the several-hid-packets-per-actual-input-packet problem,
what do you
think about constructing a special MT HID device, using raw_event?
It could
encapsulate the current protocol a bit better and use the full HID
extension.
Hi Henrik
This sounds like as a interesting direction for building a generic
driver for MT devices. However, there still are device specificities
that we need to deal with:
- the serial/parallel/hybrid issue, for which we have ideas but
still nothing firm;
- some devices need to be set in multitouch mode; we need some
research to find out if this can be determined automatically from the
report descriptors;
- the single touch emulation is highly device dependent. I was (and
still am) pretty proud of my choice of tracking the 'oldest' finger
on the panel: this turns multitouch panels into single touch panels
that are impervious to parasite touches. But the drawback is that
currently there is no generic method for this tracking: I used
whatever device-specific information I could use (order of fingers in
a message, tracking id, etc).
As long as these issues are here, we still need a system for
implementing device-specific behaviour. I must admit I was tempted to
keep benefitting from the blacklist in hid-core.c until they are
resolved.
An additional question is: how do we decide that a device is a
multitouch one? Do we keep a list of devices? Or do we rely on a
pattern found in the report descriptors? In my view it would be great
to have a pattern matching system for identifying classes of input
devices from report descriptors, but then it would reacher farther
than multitouch only.
Cheers,
St.
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