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SubjectRE: [Pcihpd-discuss] [RFC] Enhance CPCI Hot Swap driver
On Wed, 29 Jan 2003, Ed Vance wrote:

> On Tue, January 28, 2003 at 12:40 AM, Rusty Lynch wrote:
> >
> > On Tue, 2003-01-28 at 23:50, Stanley Wang wrote:
> > > Hi, Scott,
> > > After reading your CPCI Hot Swap support codes, I have a suggestion
> > > to enhance it:
> > > How about to make it be full hot swap compliant?
> > > I mean we could also do some works like "disable_slot" when
> > we receive
> > > the #ENUM & EXT signal. Hence the user could yank the hot
> > swap board
> > > without issuing command on the console.
> > > How do you think about it?
> > >
> >
> > How does this behavior translate to "full hot swap
> > compliant"? I assume
> > you are talking about wording from PICMG 2.16, which in my opinion
> > describes the full software stack, not just the driver. Any kind of
> > full CPCI solution would have all the user space components to
> > coordinate disabling a slot before the operator physically yanks the
> > board (and therefore behave as PICMG specifies). I'm not so sure the
> > driver knows enough to make a policy decision on what to do when an
> > operator bypasses the world and just yanks a board out with
> > no warning.
> How is this functionally different from ejecting a PCMCIA card in use? Is
> the driver obligated to do more than prevent a system crash and present
> errors to user level until the last close?

cPCI hotswap as defined in the PICMG 2.1 specification is a different
beast from PCMCIA because it was purposely defined to give software a
chance to do something before the device disappears. The specification
even goes so far as to say that the system is in an undefined state if
a device is yanked without waiting for the system software indicating it
is safe to do so. In reality, handling someone yanking a board is indeed
desireable, although it seems unlikely that the vast array of PCI device
drivers will ever get updated to handle it.


Scott Murray
SOMA Networks, Inc.
Toronto, Ontario

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