Subject: Re: IST_* constants
To: Charles M. Hannum <>
From: Chris G Demetriou <Chris_G_Demetriou@UX2.SP.CS.CMU.EDU>
List: tech-kern
Date: 03/27/1996 16:44:25
> It's come to my attention that some people don't understand what the
> IST_* constants are for.  I will attempt to explain their purpose
> here.
> The need for them comes from the fact that different pieces of
> hardware expect interrupts to be triggered in different ways.  It's
> very important, for example, that an IRQ being used for an
> edge-triggered device not be configured for level-trigger mode, or you
> could get a flood of spurious interrupts.
> There are two purposes to the `interrupt sharing types':
> [ ... ]

For the people who are confused:

This description makes those constants sound ... rather PC specific.
In some ways, that's not true at all; those particular types of
interrupt line (i will NOT call them IRQs in the general case 8-)
configurations and uses exist on many hardware platforms.