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SubjectRe: locking in psmouse
On Thu, Apr 29, 2004 at 07:40:17AM -0500, Dmitry Torokhov wrote:

> On Thursday 29 April 2004 04:58 am, Pavel Machek wrote:
> > Hi!
> >
> > > > psmouse-base.c does not have any locking. For example psmouse_command
> > > > could race with data coming from the mouse, resulting in problem. This
> > > > should fix it.
> > >
> > > Although I am not arguing that locking might be needed in psmouse module I
> > > am somewhat confused how it will help in case of data stream coming from the
> > > mouse... If mouse sent a byte before the kernel issue a command then it will
> > > be delivered by KBC controller and will be processed by the interrupt handler,
> > > probably messing up detection process. That's why as soon as we decide that
> > > the device behind PS/2 port is some kind of mouse we disable the stream mode.
> >
> > Does that mean that mouse can not talk while we are sending commands
> > to it? That would help a bit.
> >
> Yes, check psmouse_probe. As soon as PSMOUSE_CMD_RESET_DIS acknowledged mouse
> should cease sending motion data. That still leaves possibility of screwing up
> detection if you are moving mouse while psmouse doing PSMOUSE_CMD_GETID.
> But I don't think we can do much about it as we'd like to know that the device
> is some kind of a mouse before we start messing with it.

I've updated the atkbd_command/atkbd_interrupt mechanism so that even
bytes coming from the keyboard when we're issuing a command shouldn't
disturb us. I've tested by banging my head at the keyboard while
plugging it in. ;)

Something like that might be worth implementing for psmouse as well.

Vojtech Pavlik
SuSE Labs, SuSE CR
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