Re: [Qemu-devel] [PATCH 1/2] ps2: Clear the queue on PS/2 mouse reset and obey device disable

[geoff@hostfission.com]

On 2018-05-07 22:41, Gerd Hoffmann wrote:
> On Mon, May 07, 2018 at 10:26:24PM +1000, geoff--- via Qemu-devel 
> wrote:
>> 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 <geoff@hostfission.com>
>> > > ---
>> > >  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.
> 
> Ok.  Same check should be added to ps2_keyboard_event() then I guess?

Quite correct, I will include this in the next patch set.

> 
> cheers,
>   Gerd