How to read a timestamp in kernel driver code?

From: Mike A. Harris (mharris@meteng.on.ca)
Date: Thu Feb 24 2000 - 15:58:57 EST

I'm working on some stuff in keyboard.c that is timing sensitive
right now. What I want to do is keep track of the elapsed time
between to successive calls to handle_scancode().

How exactly would I do this? I've snooped around here and there,
and it appears that something like:

static unsigned keyb_oldtimer, keyb_newtimer;

...

blah handle_scancode(lkdsfsjdfljfas)
{
        blah blah

        keyb_oldtimer = keyb_newtimer;
        keyb_newtimer = gettimeofday();

        blah blah

        blah blah

        my code that deals with the difference in time between
        the two values
}

I'm wanting to time the difference in time between a certain
keystroke's make code being received and the break code for
comparison and timing reasons. I've looked at kernel/time.c but
that just looks like userland stuff.

I've looked at linux/timer.h, and it looks like it might have
what I'm wanting. I'm not sure exactly how I'd use it though.

Basically, I'd have a code that detects a certain "keycode" make
event, and then allocates a timer for it with kmalloc()?

struct timer_list keyb_keytimer;

Then in the kbd_init code have:

add_timer(&keyb_keytimer);
init_timer(&keyb_keytimer);

Then inside handle_scancode have:

time_before(&keyb_keytimer); for to stamp the start time, and
time_after(&keyb_keytimer); for to stamp the end time?

Then to compute the difference?

I need to also reset a timer once it is done with so that it can
be used again next time the sequence occurs.

Please show me some simple sample code for this. I'd be
greatful. Forgive me if this is an obvious thing as I'm fairly
new to kernel programming, and my manual is Luke Sourcewalker.

TIA,
TTYL 

-- 
Mike A. Harris                                     Linux advocate     
Computer Consultant                                  GNU advocate  
Capslock Consulting                          Open Source advocate

Suspicious Anagram #4:
Word:    PRESIDENT CLINTON OF THE USA
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