Date: Wed, 9 Dec 1998 09:10:01 -0800 (PST) From: Nate Williams <nate@mt.sri.com> To: freebsd-bugs@FreeBSD.ORG Subject: Re: kern/9030: DMPno2 - PCCards are not being recognised on insertion after system startup Message-ID: <199812091710.JAA06063@freefall.freebsd.org>
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The following reply was made to PR kern/9030; it has been noted by GNATS.
From: Nate Williams <nate@mt.sri.com>
To: David Pick <D.M.Pick@qmw.ac.uk>
Cc: Nate Williams <nate@mt.sri.com>, FreeBSD-gnats-submit@FreeBSD.ORG
Subject: Re: kern/9030: DMPno2 - PCCards are not being recognised on insertion
after system startup
Date: Wed, 9 Dec 1998 10:05:19 -0700
> >> >Number: 9030
> >> >Category: kern
> >> >Synopsis: DMPno2 - PCCards are not being recognised on insertion afte
> >r system startup
> >> >Confidential: no
> >> >Severity: serious
> >> >Priority: high
> >> >Responsible: freebsd-bugs
> >> >State: open
> >> >Quarter:
> >> >Keywords:
> >> >Date-Required:
> >> >Class: sw-bug
> >> >Submitter-Id: current-users
> >> >Arrival-Date: Wed Dec 9 03:30:01 PST 1998
> >> >Last-Modified:
> >> >Originator: David Pick
> >> >Organization:
> >> >Release: FreeBSD 3.0-RELEASE i386
> >> >Environment:
> >>
> >> FreeBSD 3.0 installed from Walnut Creek CDROM onto a
> >> Toshiba Libretto 50CT.
> >>
> >> >Description:
> >>
> >> PCCards are not being recognised on insertion.
> >
> >Here's a quick fix for the problem. The correct fix is to configure
> >your PCIC controller quickly. The reason this hasn't been done is
> >no-one with the ability to do it has the time to do it.
> >
> >On line 816 of /sys/pcic.c:
> > if (validslots && pcic_irq <= 0)
> >Change this to:
> > if (validslots)
> >
> >And it will work. However, you're wasting an IRQ for the PCIC
> >controller that is doing nothing for you.
>
> And indeed it *did* work. Many thanks. I must admit to some
> curiosity about how/why this causes an IRQ to be wasted, and
> if the code you advised removing was there only to prevent an
> IRQ from being wasted; but I guess I'll have to read the code
> to find out why/what is happening ( ;-) - and if I understand
> it fix it myself ( ;-) (!)
The issue is that the PCIC is assigned an interrupt to inform the kernel
of insertion/removal events. However, this interrupt is not being
generated by these events, so in effect the asignment of the interrupt
to the controller is 'wasting' an interrupt since it doesn't work.
The code in question above causes the kernel to 'poll' for
insertion/removal events, thus eliminating the need for the kernel to
get interrupts for the events. The reason this isn't the default is
because the 'interrupt' code (hopefully) reduces the race condition that
occurs when hardware is removed out from under a software driver.
Whether or not this is the case is unknown, but it's something to be
Nate
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