Re: [RFC] Microsoft Touch Mouse driver [was: Re: your mail]

[Maurus Cuelenaere <mcuelenaere@gmail.com>]

Op 07-02-12 17:12, Henrik Rydberg schreef:
>> Ok, so it's pretty clear the consensus is that there should be a
>> different interface to push the data to user space.
>> My initial reaction is V4L, as the data is basically a stream of
>> monochrome frames, this kind of fits the video description. Also,
>> this could be of some benefit to all those
>> emulate-multi-touch-using-webcam projects.
> On the other hand, your device, and the ones to come, are likely not
> normal ccd cameras, and the interface is bound to be different; you
> would most likely prefer the stream to be silent when there are no
> touches, for instance, and only generate interrupts or new-data events
> as there is something to react to.

True, I had forgotten about that. There are no HID packets sent when 
nothing touches the surface and the CPU shouldn't needlessly spent 
cycles on parsing an empty stream.

>> Other options I see are mmap on the input device, creating a
>> separate (char?) device, UIO or even having the whole thing in
>> userspace.
> Personally, I think mmapped input devices would be a great extension
> to the input subsystem. I am thinking event types distributed in a 2D
> plane, maybe one node per type, and signalled by normal input events
> of the data-to-read type.

Ok, I'll look into that!

>> However, there's one tiny hack I'd like to have and I'm unsure
>> whether this can be done from userspace: as the mouse has only one
>> physical push button, it can't distinguish between left, middle or
>> right click.
>> Obviously, it can do this based on the information it gathers from
>> its touch surface, however the firmware has only the following dumb
>> implementation: when only one finger is present on the right part of
>> the surface, assume right click; otherwise assume left click. This
>> means that you need to lift your left finger when performing a right
>> click.
>>
>> Now, the receiver is represented as 3 HID devices: one keyboard
>> descriptor, one mouse descriptor and one miscellaneous/control
>> descriptor (containing touch surface data). My plan was to intercept
>> mouse clicks on the mouse descriptor and look at what part of touch
>> surface (left/right) has the most pressure and, if needed, swap the
>> click to a right click.
>>
>> Any hints on how to do this in userspace? Of course I could hack up
>> xf86-input-evdev, but I'd like to do this at the highest possible
>> layer, ie the input subsystem.
> The application you describe could well be implemented in the driver
> you submitted; a simple handling of the MT data resulting in normal
> input events.

Yes, that was my initial idea. But as I had the impression that an 
userspace solution was preferred, I wondered how to solve that.

-- 
Maurus Cuelenaere