[ANNOUNCE] libinputmapper - Linux input-event mapping library

[David Herrmann]

Hi

Following previous discussions, I pushed some initial work for the
libinputmapper library to github. You can find the repository at:
  https://github.com/dvdhrm/libinputmapper

At the library's core, there is one important function:
  void inmap_mapping_map(struct inmap_mapping *mapping,
                                     const struct input_event *in,
                                     struct input_event *out,
                                     enum inmap_mapping_map_flags flags);
As one might guess, this function takes a linux "struct input_event",
performs some conversions/translations/.. and outputs it again. The
supported operations are currently limited to simple "ev->code" to
"ev->code" conversions. So for instance KEY_UNKNOWN can be remapped to
KEY_BACKSPACE. But this is not limited to keys, you can also remap
ABS_X to ABS_Y.

However, it does not support remapping across a single "ev->type". So
KEY_UNKNOWN cannot be remapped to LED_XY (which also wouldn't make
sense).

The main purpose is to fix broken keymaps in the kernel. We often
cannot fix them upstream for backwards compatibility reasons.
Furthermore, mapping-tables can be used to avoid cross-device
incompatibilities:
  Many Gamepads report the DPad buttons via different KEY_* codes.
Newer kernels provide BTN_DPAD_* so we could provide mapping-tables
for older gamepads to remap their DPads accordingly. Hence,
applications would no longer have to special-case old broken gamepads.

The library is supposed to be very small and efficient. Mappings other
than "code->code" can be easily added without breaking backwards
compatibility.

The library allows applications to create their own mappings
dynamically. However, it also comes with a parser for udev's hwdb.
This allows us to store any known mapping in hwdb and libinputmapper
can fetch it from there (matching is currently done via kernel
modaliases).

Note that I haven't really tested the code, yet. I wanted to push this
out so people can comment on the idea and we have something to point
to. I will pick this up after I come back from XDC. Until then I will
probably not add much to it.

Side-note: Is it ok to use "input-tools at fdo" as official mailing-list for this?

Regards
David