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Date:      Fri, 22 Jan 1999 10:09:47 +0100
From:      Poul-Henning Kamp <phk@critter.freebsd.dk>
To:        Mike Smith <mike@smith.net.au>
Cc:        Bill Trost <trost@cloud.rain.com>, mobile@FreeBSD.ORG
Subject:   Re: Reclaiming irqs for unsupported PCI hardware? 
Message-ID:  <2125.916996187@critter.freebsd.dk>
In-Reply-To: Your message of "Thu, 21 Jan 1999 17:58:34 PST." <199901220158.RAA12743@dingo.cdrom.com> 

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In message <199901220158.RAA12743@dingo.cdrom.com>, Mike Smith writes:
>> In message <199901211928.LAA10433@dingo.cdrom.com>, Mike Smith writes:
>> 
>> >Once the card is gone, all of the 
>> >registers in the mapped space read all-1s.
>> 
>> This should not be relied on.  It is my understanding that you will
>> get fireworks bus-cycles on CardBus in this situation, and it will
>> be left to the BIOS writer to figure out what should happen since
>> I belive we end up in SMM mode in that case...
>
>Cardbus is completely different.  I can hardly wait to see what happens 
>when you pull a cardbus card.

You get special bus cycles I belive, and aborted IO if you try, this 
should be catchable and if drivers are aware of it, recoverable.

>> Also I have not seen any documentation saying the all-1s is a standard,
>> but would accept a survey of pcic's which show this to be universal
>> so far.
>
>The input drivers are pulled up, IIRC, so in the absence of anything 
>driving them, and modulo noise from the card departing, I'd expect an 
>*eventaul* all-1s.  I certainly wouldn't want to rely on it though.

Well, the point is, if you could rely on it, you could do something...

>> There is no way to guarantee that the card will not be pulled in the
>> next N microseconds.
>
>Rrrg.  This is actually a really good point, and I can see where this 
>leads to.
>
> 1) DO NOT REMOVE THE CARD UNTIL YOU HAVE SHUT IT DOWN.
> 2) Poll for insertions/removals since the cards are never active in
>    either state (see point 1).
>
>Perhaps we're just looking at this the wrong way?  We don't try to 
>detect when floppies are stupidly removed, perhaps we shouldn't try to 
>do it with pccard/cardbus cards either?
>
>Commentary?  Are we trying too hard to do something that's not worth 
>the effort?

PCMCIA/PCcard is fundamentally flawed in this respect, we can add some
kludges (see "gone" in sio.c" for instance), but we can never guarantee
that it will not crash the machine.

--
Poul-Henning Kamp             FreeBSD coreteam member
phk@FreeBSD.ORG               "Real hackers run -current on their laptop."
FreeBSD -- It will take a long time before progress goes too far!

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