82 lines
3.0 KiB
Plaintext
82 lines
3.0 KiB
Plaintext
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/* $NetBSD: interrupts,v 1.1 1996/10/14 22:27:03 mark Exp $ */
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/*
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* Copyright (c) 1996 Mark Brinicombe.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Mark Brinicombe.
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* 4. The name of the company nor the name of the author may be used to
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* endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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Notes on interrupts.
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Ok since interrupts can be chained the return value from an interrupt
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handler is important.
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The following return values are defined :
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-1 - interrupt may have been for us but not sure so pass it on
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0 - interrupt no serviced (not ours)
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interrupt serviced but pass on down the chain
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1 - interrupt serviced do not pass on down the chain
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The important bit is whether the interrupt should be passed on down
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the chain of attached interrupt handlers.
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For some interrupts and drivers where only a single device is
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ever expected, the interrupt should be claimed if it has been serviced.
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Passing it on down the chain may result in the stray interrupt handler
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being called.
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There are however some interrupt that should *always* be passed on down
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the chain. These are interrupt which may commonly have multiple drivers
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attached.
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The following interrupts should always be passed on (return value of 0)
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IRQ_TIMER0
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IRQ_TIMER1
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IRQ_VSYNC
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IRQ_FLYBACK
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IRQ_PODULE
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IRQ_CLOCK (RC7500)
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The following interrupts are recommended to be passed on
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IRQ_DMACH0
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IRQ_DMACH1
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IRQ_DMACH2
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IRQ_DMACH3
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IRQ_DMASCH0
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IRQ_DMASCH1
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IRQ_SDMA (RC7500)
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All other interrupts are not expected to be shared and may be claimed
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when serviced. Stray IRQ handlers may or may not be attached to the end
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of these irq chains.
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