/*************************************************************
 * File: pmirq.c
 * Author: Phil Bunce (pjb@carmel.com)
 * Purpose:
 * 	This function makes it very easy to install interrupt handlers
 *	that are written in C. See examples/pmon/irq.c for an example
 *	of its use.
 * Revision History:
 *	961208	Created
 *	981016	Renamed. Was irq.c
 */

#include <mips.h>
#include <utypes.h>
#include <irqvec.h>

#ifndef SR_ISHIFT	/* just in case you don't have this yet */
#define SR_ISHIFT	8
#endif

int IRQTrap();
static Func *hwexctbl[] = {0,IRQTrap};


/***********************************************************************
*  Func *pmIRQInstall(int IRQNum, Func *ISRFun)
*
* Install and enable a new Interrupt Service Routine.
*
* int IRQNum - interrupt request number (0..7)
*	0 = sw0		lo priority
*	1 = sw1
*	2 = int0
*	3 = int1
*	4 = int2
*	5 = int3
*	6 = int4
*	7 = int5	hi priority
*
* Func *ISRFun - new interrupt handler
*	If ISRFun is zero, the specified vector will be uninstalled
*
* Return:
*     The old interrupt service routine address.
*/
Func *pmIRQInstall(IRQNum, ISRFun)
int IRQNum;
Func *ISRFun;
{
        Func * OldISR;

        /* Sanity check */
        if (IRQNum < 0 || IRQNum >= MAXINTHNDLRS)
                return((Func *)0);

	/* only does this the first time */
	if (hwexctbl[0]==0) onintr(0,hwexctbl);
	if (pri_table[1]==0) buildPriTable(pri_table);

        /* Get old ISR function */
        OldISR = IRQVector[IRQNum];

	if (!ISRFun) { /* uninstall */
        	mtc0(C0_SR,mfc0(C0_SR)&~(1<<(SR_ISHIFT+IRQNum)));
		IRQVector[IRQNum] = 0;
		return(OldISR);
		}

        /* Replace with new ISR function */
        IRQVector[IRQNum] = ISRFun;

        /* Enable the interrupt */
        mtc0(C0_SR,mfc0(C0_SR)|(1<<(SR_ISHIFT+IRQNum))|SR_IEC);

        return(OldISR);
}