Re: [Qemu-devel] [PATCH] [RFC] usb-wacom

[Anthony Liguori]

Hi Francois,

Can you please send the patch to the mailing list attached as a 
text/plain attachment or inlined.  Then we can review and possibly 
commit it.

Thanks,

Anthony Liguori

François Revol wrote:
> Hi there.
> We use QEMU a lot to debug Haiku, http://haiku-os.org/
> I also wrote a little php script that use it to demo images online, 
> serving a VNC java applet to connect to it with VNC.
> http://dev.haiku-os.org/browser/haiku/trunk/3rdparty/mmu_man/onlinedemo/haiku.php
> It's a bit like what live.OSZoo does, but simpler.
>
> To accomodate the VNC setup, I tried to use the usb tablet emulation. 
> It turns out Haiku has a driver for Wacom tablets:
>
> http://dev.haiku-os.org/browser/haiku/trunk/src/add-ons/kernel/drivers/input/wacom
> http://dev.haiku-os.org/browser/haiku/trunk/src/add-ons/input_server/devices/wacom
>
> However, it didn't really work very well with qemu's usb-wacom code.
>
> First, mouse stayed in the top-left corner... Seems coords were set to 
> 0,0 when no button is pressed, which is wrong, most tablets actually 
> sense the stylus even when it's not yet touching the surface.
>
> Also, coords were wrong.
> Our driver takes the pos from the hardware, and scales them from model-
> dependant hardcoded max values:
> http://dev.haiku-os.org/browser/haiku/trunk/src/add-ons/input_server/devices/wacom/TabletDevice.cpp#L115
> down to [0.0f, 1.0f], which represents the whole screen.
> Since QEMU reports absolute mouse position scaled from screen size to 
> INT16_MAX this didn't really work.
> Now, I'm not sure those max values are correct for all Penpartner 
> devices, or if they were calibrated on a specific item.
> Best would be to actually read them from the HID descriptor, but QEMU 
> doesn't provide one, and I read some penpartner tablets actually have 
> wrong descriptors anyway.
>
> Finaly, I fixed button handling according to our driver, not sure all 
> drivers handle them the same. pressure indicates left button, and a 
> flag tells about right one. I mapped middle button to the eraser to at 
> least be useful in tablet-aware software though I'm not sure it's the 
> best way.
>
> And... oh well seems we don't need to tell we have a contact, the 
> driver assumes it always for penpartner so it seems correct.
>
> I left debug macro I used just in case.
>
> http://revolf.free.fr/beos/patches/qemu-usb-wacom-for-haiku.diff.txt
>
> Now at least it works perfectly with our driver, appart from high cpu 
> usage but that's surely be fixed by polling less often.
>
> Comments ?
>
> François.
>
>
>