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

["Henrik Rydberg" <rydberg@euromail.se>]

> 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.

> 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.

> 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.

Thanks,
Henrik