From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Tue, 22 Jun 1999 02:17:52 +0000
From: Christopher Pane cpane@metamorsw.com
Subject: [9fans] Hooking up to a timer in a driver
Topicbox-Message-UUID: 9902a426-eac8-11e9-9e20-41e7f4b1d025
Message-ID: <19990622021752.LUStkY15dWTrW5UNutpHu0N-t-6-Q1j9t9rD-IhH4JQ@z>

Hi,

This is an update.

I have been hacking into how the pc kernal setups up the 8253 PIT.

It looks like if you want to get interrupted you insert a call to your
clock routine inside the clock() function in pc/clock.c.

Here is what is there now -

static void
clock(Ureg *ur, void *arg)
{
    Proc *p;
    int nrun = 0;

    USED(arg);

    m->ticks++;

    checkalarms();
    uartclock();
    hardclock();

/* And more clock stuff */

}

Is it correct to assume that if I want a clock interrupt I can  add a
midiclock() function , like the uartclock() and mouseclock() functions
that will get called every time clock is called by the timer, thus
giving me a way to sample the output queue for my file system, and
decide if is time to send the data to the MIDI port?

Am I way off here, I am kind exploring how to do this by reverse
engineering what is going on in the code !!!


Thanks


-Chris Pane