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RE: How to request an IRQ for NMI on MIPS Processor

To: Adeel Malik <>,
Subject: RE: How to request an IRQ for NMI on MIPS Processor
From: "Liu Hongming (Alan)" <>
Date: Tue, 11 Nov 2003 10:51:50 +0800
Original-recipient: rfc822;
hi Malik,

when using request_irq(...),the parameter irq is a value specified by you,
of course,when porting linux for your board,you should have specified value
for every IRQ. 0--5 only means CPU pin for interrupt,unless that only one interrupt
may occur on this pin,you will use other value in request_irq,instead of 0-5.
all in all, when we touch request_irq,it is board specific.When your board has
been made out,all interrupts have specific route to cpu(unless you have IRQ
router,since embedded,need this??).If you have more external interrupts than
cpu pins,maybe you have cascaded many interrupt using one cpu pin.So,
the parameter irq in request_irq is determined by your board and your porting
for interrupt handling.Just ask that guy that ported linux.He will tell you.If you
are using linux ported by others,have a look at BSP codes.
Alan Liu
-----Original Message-----
From: Adeel Malik []
Sent: Tuesday, November 04, 2003 7:56 PM
Subject: How to request an IRQ for NMI on MIPS Processor

Hi All,
          In my embedded design, I intend to use NMI of MIPS 4Kc processor (rather than IRQ0 or IRQ1 .....) for an external Interrupt Source. The external Interrupt source is a video capture device which interrupts the MIPS 4Kc CPU via its NMI (Non-Maskable Interrupt) line, whenever it has one complete frame. I need to write the driver for that device in Linux-2.4.20. The request_irq function provided by Linux takes a digit value from 0 to 5 to map external interrupt sources to any one of CPUs Interrupt pins. How can I request and implement my interrupt handler routine for the NMI of MIPS processor ?.

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