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From: jeh@cmkrnl.com (Jamie Hanrahan)
Newsgroups: comp.os.ms-windows.programmer.nt.kernel-mode
Subject: Re: Various beginner questions on DDKs
Message-ID: <1998Jan14.161913.8410@cmkrnl>
Date: 14 Jan 98 16:19:13 PST
References: <69fmvs$b2v$1@smilodon.ecp.fr>
Organization: Kernel Mode Systems, San Diego, CA
Lines: 86

In article <69fmvs$b2v$1@smilodon.ecp.fr>, riad@cti.ecp.fr (El Gringo) writes:
> 1- How to synchronize two different ISR ? (different DIRQL levels)

This is fairly simple to set up.  

You need to have storage for a spinlock and for an a array 
of pointers to interrupt objects in your device extension (or 
somewhere else convenient).  Then assuming that in irq[] you have the 
IRQs you want to connect to:

// in the device extension
typedef struct _MY_DVC_EXT {
	...
	KSPIN_LOCK	InterruptSpinLock;
	PKINTERRUPT_OBJECT	IntObj[n];
}

// allocate some temporaries

KIRQL	highIrql;
KIRQL	irql[nInts];
KAFFINITY affinity[nInts];
ULONG	vec[nInts];

// initialize our spinlock

KeInitializeSpinLock ( &dvcExt->InterruptSpinLock );

// do all the HalGetInterruptVector calls, saving the returned vectors,
// dIRQLs, and affinities in arrays, and tracking the highest dIRQL

highIrql = PASSIVE_LEVEL;

for ( i = 0 ; i < nInts ; i++) {
	vec[i] = 
	 HalGetInterruptVector(
	 Isa, 0, 	// whatever
	 irq[i], 	// the input interrupt "level" (IRQ)
	 irq[i], 	// the input interrupt "vector" (same as level for 
			//  PC buses)
	 &irql[i],	// the output IRQL
	 &affinity[i]);	// the output affinity mask

	if (irql[i] > highIrql) highIrql = irql[i];
}

// now connect to all of the interrupts, passing the respective
// IRQL, affinity, and vector. For SynchIrql, use the highest of
// all of the IRQLs.  For the spinlock argument, use the 
// driver-supplied spinlock.  This way, all interrupt objects
// have the same SynchIrql, and all point to the same spinlock.

for ( i = 0 ; i < nInts ; i++) {
	IoConnectInterrupt (
	 &dvcExt->IntObj[i], 	// save the returned interrupt object addresses
	 MyIsr,			// you could use a different ISR entry point for each interrupt
	 dvcObj, 		// likewise, you could use a different ISR context for each interrupt
	 &dvcExt->InterruptSpinLock, 	// common interrupt object spinlock for all of our interrupts
	 vec[i], 		// the vector for this interrupt
	 irql[i], 		// the IRQL for this interrupt
	 highIrql,		// the highest of all our interrupts' IRQLs
	 interruptMode, 	// as appropriate
	 shareVector, 		// as appropriate
	 affinity[i], 		// the affinity mask for this interrupt
	 floatingSave);		// as appropriate
}

Then:

All of the ISRs for all of the interrupts will be serialized with
respect to each other, and also with respect to any SynchCritSection
routines invoked via KeSynchronizeExecution used with ANY of the
returned interrupt objects. 

Source: KMD Design Guide, section 3.5.2 and 8.1.3, plus a bit of 
intuition and reading between the lines.  

Note, don't pass &dvcExt->InterruptObjectSpinlock to 
KeAcquireSpinLock!

	--- Jamie Hanrahan, Kernel Mode Systems, San Diego CA
        Internet: jeh@cmkrnl.com (JH645)  CompuServe: 74140,2055  
drivers, internals, networks, applications, and training for VMS and Windows NT
NT driver FAQ, links, and other information:  http://www.cmkrnl.com/

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