On 2018-05-07 22:21, Gerd Hoffmann wrote:
> On Mon, May 07, 2018 at 10:00:22PM +1000, geoff--- via Qemu-devel wrote:
> > This allows guest's to correctly reinitialize and identify the mouse
> > should the guest decide to re-scan or reset during mouse input events.
> >
> > Signed-off-by: Geoffrey McRae <address@hidden>
> > ---
> > hw/input/ps2.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/hw/input/ps2.c b/hw/input/ps2.c
> > index 06f5d2ac4a..6edf046820 100644
> > --- a/hw/input/ps2.c
> > +++ b/hw/input/ps2.c
> > @@ -673,6 +673,9 @@ static void ps2_mouse_sync(DeviceState *dev)
> > {
> > PS2MouseState *s = (PS2MouseState *)dev;
> >
> > + if (!(s->mouse_status & MOUSE_STATUS_ENABLED))
> > + return;
> > +
>
> Why this is needed?
To quote:
https://wiki.osdev.org/%228042%22_PS/2_Controller#Detecting_PS.2F2_Device_Types
The device should respond to the "identify" command by sending a
sequence of
none, one or two identification bytes. However, if you just send the
"identify" command you can't prevent the response from the "identify"
command from being mixed up with keyboard/mouse data. To fix this
problem,
you need to send the "disable scanning" command first. Disabling
scanning
means that the device ignores the user (e.g. keyboards ignore
keypresses,
mice ignore mouse movement and button presses, etc) and won't send
data to
mess your device identification code up.