Re: Touch processing on host CPU

[Nick Dyer <nick.dyer@itdev.co.uk>]

On 21/10/14 13:22, One Thousand Gnomes wrote:
>> If you will have touch processing in a binary blob, you'll also be going
>> to ages "Works with Ubuntu 12.04 on x86_32!" (and nothing else), or
>> "Android 5.1.2 on Tegra Blah (build 78912KT)" (and nothing else).
> 
> As well as not going upstream because there is no way anyone else can
> test changes to the code, or support it. Plus of course there are those
> awkward questions around derivative work boundaries that it is best the
> base kernel keeps well clear of.
> 
> If the data format is documented to the point someone can go write their
> own touch processor for the bitstream then that really deals with it
> anyway. Given the number of these things starting to pop up it would
> probably be good if someone did produce an open source processing engine
> for touch sensor streams as it shouldn't take long before its better than
> all the non-free ones 8).

Thank you for this input, I will feed it back.

> Given how latency sensitive touch is and the continual data stream I
> would be inclined to think that the basic processing might be better in
> kernel and then as an input device - providing it can be simple enough to
> want to put kernel side.

I would think that a touch processing algorithm (including aspects such as
noise and false touch suppression, etc) would be too complex to live
in-kernel. Getting decent performance on a particular device requires a lot
of tuning/customisation.

> Otherwise I'd say your bitstream is probably something like ADC data and
> belongs in IIO (which should also help people to have one processing
> agent for multiple designs of touch, SPI controllers etc)

This sounds promising. The only sticking point I can see is that a touch
frontend has many more channels (possibly thousands), which would seem to
impose a lot of overhead when put into the IIO framework. I will certainly
take a closer look at it.