Re: [PATCH 5/5] HID: sony: Handle multiple touch events input record

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

Hi Roderick,

[sorry for the late reply, I was on PTO until today]

On Oct 18 2016 or thereabouts, Roderick Colenbrander wrote:
> >
> > > Correct, the DS4 sends a touch history. The last element is the
> > > latest. An input report can contain multiple touch samples, because
> > > the device internally samples at a rate which is higher than at which
> > > it generates HID reports. On USB you can easily see multiple touch
> > > events and it is even easier on Bluetooth (especially if it is set to
> > > a low frequency). The extra history is important for gestures.
> >
> > OK, so if it's important, you need to actually send it by adding
> > input_mt_sync_frame() and input_sync() calls. Otherwise, the values will
> > just get mangled by the kernel in evdev and everything happens as if you
> > just sent the last pair in the history.
> >
> > The first 4 patches are IMO mergeable, but this one will need a little
> > bit more polish to actually forward the events.
> >
> > Cheers,
> > Benjamin
> >
> > >
> > > Thanks,
> > > Roderick
> 
> Hi Ben,
> 
> A kind of follow-up to this patch feedback which made it into the
> final patch. The recommendation was to use input_mt_sync_frame, which
> was a good recommendation. There is one oversight, which I'm not sure
> how we need to handle. Basically input_mt_sync_frame triggers pointer
> emulation, which is a problem for the Dualshock 4 since it already
> provides an ABS_X / ABS_Y, so the pointer emulation affects the analog
> stick values.

Ouch, sorry, I did not realize this :(

> 
> The hid-sony driver registers the touchpad through input_mt_init_slots
> with the flags parameter '0', which was intended not to request such
> emulation I think. I'm not too familiar with the other input code, but
> should input_mt_sync_frame gate pointer emulation based on
> INPUT_MT_POINTER / INPUT_MT_DIRECT flags or something like that?

I'd say so, though I need to check the other thread first.

Cheers,
Benjamin

> 
> Thanks,
> Roderick