Re: Handling of non-positional data through evdev

[David Herrmann <dh.herrmann@gmail.com>]

Hi

On Wed, Mar 16, 2016 at 4:10 PM, Bastien Nocera <hadess@hadess.net> wrote:
> On Tue, 2016-03-15 at 17:17 -0700, Roderick Colenbrander wrote:
>> Hi Bastien,
>>
>> Thanks for providing this suggestion. I can see this approach work
>> for
>> situations like screen rotation on tablets. The device I'm involved
>> with is an input device, which needs a high poll rate for
>> acceleration
>> / velocity and needs to be paired with the button / axes data. Evdev
>> would be most appropriate.
>
> So more like a Wiimote than a builtin sensor. What will consume events
> in user-space? A specialised application?

I really think evdev is the right place to put any of those devices.
The real problem is that the current set of ABS types is very limited
and strongly overloaded. We didn't do this for other types, but
somehow ABS turned out that way.

In general, Dmitry was ok with introducing new ABS types, properly
representing those types. I sent an RFC some years ago, which also
introduces gyro and accelerometer types (see patch #4):

https://lists.freedesktop.org/archives/input-tools/2013-December/000612.html

The problem is, however, that the current ABS_* namespace is
exhausted. That is, we have to introduce some new way to add new ABS
types (the series introduced ABS2 for that). No-one continued that
effort so far, so we are stuck with the current ABS types. Feel free
to pick this up. It might be a lengthy effort, though. You might be
better off doing it the wiimote way: pick you ABS types and make
user-space recognize them depending on the device name/etc.

Thanks
David