Re: PCI Hot Plug Operation

Re: PCI Hot Plug Operation

[Greg KH]

On Fri, May 03, 2002 at 11:00:10AM -0500, Bill Bruce wrote:
> My situation:
> 
> The software base is Redhat 7.2. The kernel has been updated to 2.4.9. The
> user-space hot plug files/scripts dated 2002_4_1 from SourceForge have been
> installed.
> 
> I install a PCI card in my system and power it up. It appears on the PCI bus
> (lspci -H1 confirms this).
> 
> There is no driver for this card in the kernel, but according to my reading
> of the hot plug documentation I expect the /sbin/hotplug script to be
> invoked, giving me an opportunity to load a driver. This is not happening.

/sbin/hotplug is not envoked at the first scanning of the PCI bus.  This
might be considered a bug, but as there is no userspace set up at this
point in time, any call out to /sbin/hotplug would not work anyway :)

This will be fixed in 2.5, when we have initramfs working.

> Some rudimentary questions:
> 
> I am assuming the kernel is periodically scanning the PCI bus, looking for
> new devices. Is this correct? If so how often does this happen?

No, this is not happening.

> Do I need to install a driver for my card to make the kernel aware of a
> possible hot pluggable device?

PCI Hotplug only works if you have a PCI Hotplug controller on your
motherboard.  This is usually only on high end servers or cPCI machines.
Do you have such a machine?

If not, you need to manually load the kernel module for your pci device,
sorry, as there are no "hotplug" pci events able to be generated.

I've posted a small module that manually rescans the pci bus and allows
events to be generated if it sees a new device, but this is a bit of a
hack :)  Check the archives if you're interested.

thanks,

greg k-h

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Re: PCI Hot Plug Operation

[Greg KH]

On Fri, May 03, 2002 at 06:33:45PM +0200, Gioele Barabucci wrote:
> On Friday 03 May 2002 17:16, Greg KH wrote:
> > > Do I need to install a driver for my card to make the kernel aware of a
> > > possible hot pluggable device?
> >
> > PCI Hotplug only works if you have a PCI Hotplug controller on your
> > motherboard.  This is usually only on high end servers or cPCI machines.
> > Do you have such a machine?
> >
> > If not, you need to manually load the kernel module for your pci device,
> > sorry, as there are no "hotplug" pci events able to be generated.
> I think most mb will fry if you insert a pci device while they are on...

Very true, I didn't say for him to do this :)

greg k-h

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PCI Hot Plug Operation

[Bill Bruce]

My situation:

The software base is Redhat 7.2. The kernel has been updated to 2.4.9. The
user-space hot plug files/scripts dated 2002_4_1 from SourceForge have been
installed.

I install a PCI card in my system and power it up. It appears on the PCI bus
(lspci -H1 confirms this).

There is no driver for this card in the kernel, but according to my reading
of the hot plug documentation I expect the /sbin/hotplug script to be
invoked, giving me an opportunity to load a driver. This is not happening.

Some rudimentary questions:

I am assuming the kernel is periodically scanning the PCI bus, looking for
new devices. Is this correct? If so how often does this happen?

Do I need to install a driver for my card to make the kernel aware of a
possible hot pluggable device?

Thanks

Bill Bruce
Terago Communications



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Re: PCI Hot Plug Operation

[Greg KH]

On Fri, May 03, 2002 at 10:48:23AM -0700, Stephen Williams wrote:
> 
> greg@kroah.com said:
> > I've posted a small module that manually rescans the pci bus and
> > allows events to be generated if it sees a new device, but this is a
> > bit of a hack :)  Check the archives if you're interested. 
> 
> This is interesting. Does this mean that if I install a new PCI
> device (I have an isolating extender with a power switch) I can
> add a new device to a running system? It will get mapped?

Yes.  See this driver:
	http://marc.theaimsgroup.com/?l=linux-hotplug-devel&m\x101312609603679
and the other messages in that thread for more information.

thanks,

greg k-h

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Re: PCI Hot Plug Operation

[Stephen Williams]

greg@kroah.com said:
> I've posted a small module that manually rescans the pci bus and
> allows events to be generated if it sees a new device, but this is a
> bit of a hack :)  Check the archives if you're interested. 

This is interesting. Does this mean that if I install a new PCI
device (I have an isolating extender with a power switch) I can
add a new device to a running system? It will get mapped?
-- 
Steve Williams                "The woods are lovely, dark and deep.
steve at icarus.com           But I have promises to keep,
steve at picturel.com         and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."

abuse@xo.com
uce@ftc.gov



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Re: PCI Hot Plug Operation

[Paul Hedderly]

On Fri, May 03, 2002 at 08:16:25AM -0700, Greg KH wrote:
> PCI Hotplug only works if you have a PCI Hotplug controller on your
> motherboard.  This is usually only on high end servers or cPCI machines.
> Do you have such a machine?

Well, there are other machines that pci hotplug could work on - laptops.

Many have docking stations that add an extra pci bus through a bridge...
it would be really nice to be able to "hot" add that bus, and "hot"
remove it - provided devices on it were not in use.

The IBM laptops do this very well, but I don't think linux supports this
kind of functionality... yet? Is it possible? Is anyone working on it?

--
Cheers
Paul

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Re: PCI Hot Plug Operation

[David Woodhouse]

paul@mjr.org said:
>  Many have docking stations that add an extra pci bus through a
> bridge... it would be really nice to be able to "hot" add that bus,
> and "hot" remove it - provided devices on it were not in use. 

If you remove the laptop from the docking station, the PCI devices are no
longer in use. Whether you like it or not.

--
dwmw2



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Re: PCI Hot Plug Operation

[Greg KH]

On Mon, May 06, 2002 at 10:16:08AM -0700, David Brownell wrote:
> > > Do I need to install a driver for my card to make the kernel aware of a
> > > possible hot pluggable device?
> > 
> > PCI Hotplug only works if you have a PCI Hotplug controller on your
> > motherboard.  This is usually only on high end servers or cPCI machines.
> > Do you have such a machine?
> 
> Erm, when did that change?
> 
> There might be confusion about the several different types of PCI hotplug
> that can happen.  It started out as a generic term in Linux, not specific
> to a specific technology.

<snip>

Good clarification here, sorry about that.  I was thinking about the
"PCI Hotplug Support" as the "PCI Hotplug Spec" describes it, as that's
what I deal with all day long at my job.

Again, sorry for any confusion.

thanks,

greg k-h

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Re: PCI Hot Plug Operation

[David Brownell]

> > Do I need to install a driver for my card to make the kernel aware of a
> > possible hot pluggable device?
> 
> PCI Hotplug only works if you have a PCI Hotplug controller on your
> motherboard.  This is usually only on high end servers or cPCI machines.
> Do you have such a machine?

Erm, when did that change?

There might be confusion about the several different types of PCI hotplug
that can happen.  It started out as a generic term in Linux, not specific
to a specific technology.

    - The original Linux PCI hotplug support worked well for CardBus.
      Plug in a new CardBus device ("PC-Card" form factor with PCI
      bus, often mis-termed PCMCIA) and get a hotplug event.

    - Docking station support ... I'm not clear what the status here
      is, but some of them support CardBus, so they should inherit
      a certain level of hotplug support from that.

    - Compaq's "PCI Hotplug" support is, as Greg said, for higher
      end hardware ... aiming at "more nines than usual" availability.

    - The "Compact PCI" stuff is a different form factor (VME?) that
      is likewise targetted at high availability applications, where it
      is not practical to take systems down to reconfigure hardware.

Admittedly you need to configure the support for those kinds of
bus into your system, but "/sbin/hotplug pci" can be invoked without
any "PCI Hotplug" (or CompactPCI) controller ... laptops do it.

- Dave



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