Re: MOUSE_PS2_VMMOUSE and input/mice

[Thomas Hellstrom <thellstrom@vmware.com>]

On 01/15/2016 12:23 PM, Lauri Kasanen wrote:
> On Fri, 15 Jan 2016 12:08:51 +0100
> Thomas Hellstrom <thellstrom@vmware.com> wrote:
>
>>> Seems the new and shiny VMWare mouse driver does not pass events
>>> to /dev/input/mice, rudely breaking userspace that doesn't
>>> support absolute input devices.
>>>
>>> Can this be changed? Would there be any downside to passing those
>>> events?
>> Hi, Lauri.
>> What particular use-case is broken?
> VMWare + 4.2 kernel + Xvesa. This was reported for the current TinyCore
> beta, which has that kernel.
>
>> I'm assuming what's happening is that only the relative device gets
>> recognized as a mouse, and by default we don't send events through that
>> device.
>>
>> In the vmware gui there is a workaround, one can select 
>> edit->preferences->input->"Optimize mouse for games"->Always
>>
>> This will send events through the relative USB mouse, and if there is no
>> USB controller in the VM, through the relative MOUSE_PS2_VMMOUSE
>>
>> The other option is to limit the number of protocols the PS2 driver
>> checks for and avoid enabling the vmmmouse functionality. There is a
>> kernel module option for that, although I can't remember it offhand.
>>
>> We can't send both relative and absolute events simultaneously since
>> that would confuse the X server severely.
> Yeah, I know of the psmouse.proto=imps workaround. But requiring either
> bootcodes or VM setting tweaks is not nice, as what the users see will
> be "distro version X worked in my VMWare, in version Y the mouse does
> not work".
>
> If we instead disable MOUSE_PS2_VMMOUSE, I assume a future
> xf86-input-vmmouse version will drop support for the userspace-side
> mouse synchronization, and then VMWare+Xorg users will suffer.

At present, MOUSE_PS2_VMMOUSE is only needed if you need to support
rootless Xorg or a native compositor without vmmouse driver in absolute
mode, like gnome-shell/wayland. If you're fine with that, perhaps
disabling the in-kernel vmmouse driver is the best option for now.
xf86-input-vmmouse will remain as-is for the forseeable future.

Guessing what protocol the client needs is always tricky. What we could
perhaps do is to try to detect the number of open clients on the
absolute mouse device and if == 0 tell the host to send relative events.
However, the host is not required to obey that request and I'm not sure
KVM/QEMU even implements that. One option would perhaps be to turn off
vmmouse and just forward ps2 data in that case.

However, I'm not sure there are hooks in the ps2 driver to detect the
number of open clients for a particular device...

/Thomas
>
> Can you think of any solution that would detect things at runtime?
>
> - Lauri