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Date: Sun, 24 Nov 2002 01:39:44 -0800
From: george anzinger <george@mvista.com>
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To: arun4linux <arun4linux@indiatimes.com>
CC: John K Luebs <jkluebs@luebsphoto.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: switching to interrupt contex when no interrupts
References: <200211231948.BAA22590@WS0005.indiatimes.com>
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arun4linux wrote:
> 
> Hello,
> 
> <<One is forced to run in interrupt context in an
> interrupt handler.
> >>Yes. But my requirement is to force my code to run in interrupt context.
> 
> <<Possibility is undefined here because what you said makes no sense.
> 
> You will get a better answer from the list if you describe what you are trying to do (in concrete terms), not how you think you might do it.
> 
> >>My requirement is to simulate a PCI based controller and its behaviour in software. I knew the different type of interrupts and the timings my device produces.
> 
> I need to simulate this PCI device, its interrupts in sequence and I have to process them in my driver software.
> 
>   Hope this make sense now.
> 
>   Anyway, my requrirement is to simulate the interrupts and process them in the interrupt context.
> 
>   It would be helpful, if anyone could help me how to do it.
>   My idea is to use task queues and bottom halves for this. But I'd like to get clarified on simulating interrupts (rasing the process/task context to interrupt context) and its consequences.
> 
Why simulate the interrupts when you can just program them? 
On the x86 machine the "int x" instruction generates an
interrupt to irq "x"+32.  You do need to be in kernel land
to do this, but then I assume that is not a problem.

-g


> 
> Thanks & Warm Regards
> Arun
> 
> "John K Luebs" wrote:
> 
> On Sat, Nov 23, 2002 at 07:37:33AM +0530, arun4linux wrote:
> &gt; Hello,
> &gt;
> &gt; I'd like to force my kernel module to run at interrupt context at some specific points/time and then come back from interrrupt contex after executing that particular portion of code..
> 
> You seem to be over complexifying what interrupt context is. It is
> simply a generic term for a context that executes on account of an
> architecture interrupt. One is forced to run in interrupt context in an
> interrupt handler.
> 
> You "run" in interrupt context by calling request_irq attached to the
> interrupt line that you are interested in installing a handler for.
> 
> &gt;
> &gt; Is it possible?
> 
> Possibility is undefined here because what you said makes no sense.
> 
> You will get a better answer from the list if you describe what you are
> trying to do (in concrete terms), not how you think you might do it.
> 
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-- 
George Anzinger   george@mvista.com
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