HID input dealing with multiple collections?

Hello,

I've written a USB device which supports multiple input devices:
* A touch surface digitizer (following Microsoft's specification)
* A pen surface digitizer
* A mouse emulator

In windows each of these interfaces are exposed as a separate top level
collection, e.g.:
Usage_Page(Generic Desktop)
Usage(Mouse)
Collection(Application)

       ...
  End_Collection
  Usage_Page(Digitzer)
  Usage(Touch_Screen)
  Collection(Application)
     ...
  End_Collection
  Usage(Digitizer)
  Usage(Pen)
  Collection(Application)
     ...

End_Collection

Now this descriptor works well in Windows; all reporting channels are
exposed correctly as hid devices and mouse/multitouch/pen input all works correctly as expected. In linux, however, this is not the case. What I see is that if I drop out the touch/pen functionality then the mouse support works correctly. Likewise, if I drop any pair of other top level collections such that I have exactly one top level collection the system works correctly.

Am I missing something here - as in: Have I made an error in my usage of
top level collections, or is linux-input's hid support incapable of dealing with multiple top level collections?

Hi,

Quoted 33 lines · Breton M. Saunders

Hello,

I've written a USB device which supports multiple input devices:
* A touch surface digitizer (following Microsoft's specification)
* A pen surface digitizer
* A mouse emulator

In windows each of these interfaces are exposed as a separate top level
collection, e.g.:

   Usage_Page(Generic Desktop)
   Usage(Mouse)
   Collection(Application)
        ...
   End_Collection
   Usage_Page(Digitzer)
   Usage(Touch_Screen)
   Collection(Application)
      ...
   End_Collection
   Usage(Digitizer)
   Usage(Pen)
   Collection(Application)
      ...
   End_Collection

   Now this descriptor works well in Windows; all reporting channels are

exposed correctly as hid devices and mouse/multitouch/pen input all works correctly as expected. In linux, however, this is not the case. What I see is that if I drop out the touch/pen functionality then the mouse support works correctly. Likewise, if I drop any pair of other top level collections such that I have exactly one top level collection the system works correctly.

Quoted 3 lines

Am I missing something here - as in: Have I made an error in my usage of
top level collections, or is linux-input's hid support incapable of dealing with multiple top level collections?

If it works under Windows, there are huge chances that your report descriptor is good.

However, under Linux, we use the report IDs to split (if required) the different inputs.
The good thing for you is that if I understand correctly, the device you are talking about should be handled through hid-multitouch. Since kernel v3.10, we have introduced the support of devices showing both a digitizer and a pen (they will show up as two input devices).

I would encourage you to test a 3.10 kernel, and/or send me some traces of your devices by using hid-replay[1]. This way I will be able to test your device on my laptop, and eventually figure out any problem.

Cheers,

Quoted 57 lines · Benjamin Tissoires

Hi,

Quoted 36 lines · Breton M. Saunders

Hello,

I've written a USB device which supports multiple input devices:
* A touch surface digitizer (following Microsoft's specification)
* A pen surface digitizer
* A mouse emulator

In windows each of these interfaces are exposed as a separate top
level
collection, e.g.:

   Usage_Page(Generic Desktop)
   Usage(Mouse)
   Collection(Application)
        ...
   End_Collection
   Usage_Page(Digitzer)
   Usage(Touch_Screen)
   Collection(Application)
      ...
   End_Collection
   Usage(Digitizer)
   Usage(Pen)
   Collection(Application)
      ...
   End_Collection

   Now this descriptor works well in Windows; all reporting channels are

exposed correctly as hid devices and mouse/multitouch/pen input all works correctly as expected. In linux, however, this is not the case. What I see
is that if I drop out the touch/pen functionality then the mouse support works correctly. Likewise, if I drop any pair of other top level collections such that I have exactly one top level collection the system works correctly.

Quoted 5 lines

Am I missing something here - as in: Have I made an error in my usage
of
top level collections, or is linux-input's hid support incapable of dealing
with multiple top level collections?

If it works under Windows, there are huge chances that your report descriptor is good.

However, under Linux, we use the report IDs to split (if required) the different inputs.
The good thing for you is that if I understand correctly, the device you are talking about should be handled through hid-multitouch. Since kernel v3.10, we have introduced the support of devices showing both a digitizer and a pen (they will show up as two input devices).

Quoted 6 lines

I would encourage you to test a 3.10 kernel, and/or send me some traces of your devices by using hid-replay[1]. This way I will be able to test your device on my laptop, and eventually figure out any problem.

Cheers,

Hi Benjamin,

Thanks for the quick reply.

3.10 is a no-go for me; I need to get this working on a vanilla (or
upgraded) version of Ubuntu 12.04; so something more like kernel version 3.2. (Unfortunately, its what people are using in the field).

I will, however, install a more modern kernel to test against; esp. since
I note your HID-replay tool requires 3.6 to test with.

Would the correct approach here be to implement a composite USB device and
have separate USB interfaces for mouse, touch and pen for compatibility with older kernel revisions?

You can still try to use my backport available here:
https://github.com/bentiss/hid-multitouch

it _should_ work on a 3.2. You only have to add your VID/PID in hid-multitouch to make it work.

Quoted 3 lines

I will, however, install a more modern kernel to test against; esp. since
I note your HID-replay tool requires 3.6 to test with.

well, it requires the module uhid, which is available in 3.6, but also in my backport :)
run "modprobe uhid_compat" and run hid-replay against the /dev/hidraw-compatN device.

Anyway, if this is too much of a pain, just send me the report descriptor in hexadecimal (and some hexadecimal captures of your events), I'll do the formatting myself.

Quoted 3 lines

Would the correct approach here be to implement a composite USB device and
have separate USB interfaces for mouse, touch and pen for compatibility with older kernel revisions?

I would say no because I don't know what would be the behavior of Windows. But if you don't care about Windows and if this solution works, it's entirely up to you.