Re: Hot Plug I/O Node spec 0.2.1

[Greg KH <greg@kroah.com>]

On Tue, Feb 05, 2002 at 02:16:20PM +0900, Hiroshi Aono wrote:
> At Sun, 3 Feb 2002 00:19:15 -0800, Greg KH wrote:
> > 
> > What is the "Object Redistration Interface" going to look like?  What is
> > needed to be sent from a configuration file to the IO Node resource
> > manager?  Doesn't the IO Node resource manager get all of the
> > information it needs from the BIOS/ACPI interface?
> 
> I expect that this mainly works for debugging.
> I think the hardware like this may not work sufficiently at first.
> or it may be used for non-ACPI machine.
> This configuration file will be stored hardware information.

Like what?  A snapshot of the device tree that was present the last time
we powered down?

> Of course IO Node resource manager should get all information from
> BIOS/ACPI.
> I think the IO node driver and the Object Registration
> interface between IO node resource manager should have same interface.

And what do you see that interface being?  

> > "pic"?  What is this?
> 
> "pic" means programmable interrupt controller like an IOSAPIC.

Ok, but why does it need to have an entry in the filesystem?  Can you
turn it on and off, with the same kinds of attributes the slots have?

> > How?  Doesn't a IO node just show up as a PCI device being added to the
> > system?
> 
> Our IO node doesn't show up as a PCI device.
> Does IBM work so?

No, the IO node never shows up at all, from what I can tell.  But all of
the pci devices show up all at once :)

> I can know the hardware structure through ACPI name space in advance.

Ah, that's nice.

> > Doesn't the PCI Hotplug driver have to be loaded to recognize that a IO
> > node was inserted into the system?
> 
> If so, I think PCI hotplug driver should be loaded in advance.

I agree.

> > > Conversely, when an IO node is removed, a script for IO node will be
> > > executed and the PCI hotplug driver will stop all PCI devices under
> > > the IO node.
> > 
> > Will the removal event fire for every PCI slot, or just once for the
> > node?  If just once, I now understand why you need this IO node driver :)
> 
> Yes, I think it's just once.

Ok, that makes sense.

> > I am not aware of any other method of getting this information.  I
> > thought the BIOS _had_ to do this.  Is there another way of doing this?
> 
> This means we can specify the IO/Memory space gap and bus numbers on a BIOS
> menu.
> I think this is same rule for PCI hotplug. Is this right?

Yes, for the hardware that I have seen.


> > IBM's BIOS does not work this way.  Does this matter?  On insertion, it
> > only notifies the OS when the card has been powered up and configured
> > (skipping steps 2 and 3 above).  If an error occured when configuring
> > (bus speed mismatch, etc.) this error is reported.  Then the OS can
> > assign physical resources, call /sbin/hotplug with the notification that
> > a new device has been seen, and allows the driver to be loaded.
> 
> Actually, hardware spec doesn't fix yet, so we can suggest this for our
> hardware people.
> Personally, I feel that we don't need steps 2 and 3.

I agree.

> > Most of the removal steps are not present too.  The BIOS does most of
> > it, and again, only notifies the OS when everything is done.
> > 
> > Because of this, a number of places where you will be notifing the OS
> > user of something, the IBM driver can not.  Do you see this being a
> > problem?
> 
> I feel those hardware dependency part should be implement as a local IO node
> driver.

Ok, I understand the need for a hardware specific driver.  Your NEC ACPI
PCI Hotplug driver will look different than the IBM ACPI PCI Hotplug
driver, just due to the differences in ACPI implemenation of the
different BIOSs.


> I think it will be ok if we decide the interface definitely between IO
> node driver and IO node resource manager.

Ok, I guess I'll just have to see some code to understand this interface :)

thanks,

greg k-h

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