Re: getting timestamp of last interrupt?

[Hans-Georg Thien]

Richard B. Johnson wrote:

> On Mon, 6 Oct 2003, Hans-Georg Thien wrote:
>
>
> > Richard B. Johnson wrote:
> >
> >
> > > On Mon, 6 Oct 2003, Hans-Georg Thien wrote:
> > >
> > >
> > > > [...]
> > > > I'm writing a kernel mode device driver (mouse).
> > > >
> > > > In that device driver I need the timestamp of the last event for another
> > > > kernel mode device (keyboard).
> > > >
> > > > I do not care if that timestamp is in jiffies or in gettimeofday()
> > > > format or whatever format does exist in the world. I am absolutely sure
> > > > I can convert it somehow to fit my needs.
> > > >
> > > > But since it is a kernel mode driver it can not -AFAIK- use the signal()
> > > > syscall.
> > > >
> > > > -Hans
> > >
> > >
> > > Then it gets real simple. Just use jiffies, if you can stand the [...]
> >
> > I fear that there is still some miss-understanding. Jiffies are totally
> > OK for me. I can use them without any conversion.
> >
> > I'll try to formulate the problem with some other words:
> >
> > I hope that there is is something like a "jiffie-counter" for the
> > keyboard driver, that stores the actual jiffies value whenever a
> > keyboard interrupt occurs.
>
>
> Well the keyboard driver and the mouse driver are entirely
> different devices.
yes, - I know

> The keyboard has a built-int CPU that generates scan-codes for
> every key-press/key-release. It also performs auto-repeat. The
> mouse generates mouse data at each interrupting event. This data
> represents direction and three key events. Wheel mouse have may
> have additional data, I haven't looked at them. They are not
> related in any way.
yes, - I know

> > I hope too, that there is a way to query that "jiffie-counter" from
> > another kernel driver, so that I can write something like
> >
> >
> > mymouse_module.c
> >
> > ...
> > void mouse_event(){
> >
> >    // get the current time in jiffies
> >    int now=jiffies;
> >
> >    // get the jiffie value of the last kbd event
> >    int last_kbd_event= ????;  // ... but how to do that ...
> >
> >    if ((now - last_kbd_event) > delay) {
> > 	do_some_very_smart_things();
> >    }
> >   }
> > ...
>
>
> Now this pseudo-code shows a "last_kbd_event", not a mouse-
> event as shown in:
yes, - I know =8))

It is because I want do some things with the mouse in relation to 
keyboard events.

> [... a quite detailed explanation on mouse interrupts, mouse data ...]
yes, I know. But my question was: how can I get the timestamp of the 
last keyboard interrupt.

> When your module is un-installed, it needs to restore the
> previous (saved) value of that pointer.
yes, - I know

> Whatever code you make that pointer point-to, must be
> interrupt-safe. It can get the jiffie-count and put it
> into a buffer, then return.
yes, - I know

Hey Richard, - what is so difficult to understand ?

Anyway, - have you read the email reply from Gabriel Paubert regarding 
this topic? Sounds very good for a 2.6.x kernel. It seems that I can use 
the /dev/input/event? device files. I have just modprobed the "evdev" 
module. It seems that I can get my timestamps by reading one of this 
files. Have to investigate still which one of them I have to use.

-Hans


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