Re: HID input dealing with multiple collections?

["Breton M. Saunders" <bms20@brettnet.eu>]

On 09/09/13 14:12, Benjamin Tissoires wrote:
> Hi,
>
> On Mon, Sep 9, 2013 at 2:56 PM, Breton M. Saunders <bms20@brettnet.eu> wrote:
>> 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?
> 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,
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?

     Cheers,

     -Brett