Re: How to find hotplug slot of PCI dev?

[Linas Vepstas <linas@austin.ibm.com>]

On Wed, Jun 29, 2005 at 03:44:38PM -0700, Greg KH was heard to remark:
> On Wed, Jun 29, 2005 at 05:05:08PM -0500, Linas Vepstas wrote:
> > 
> > Hi,
> > 
> > I can't think of any easy way of (generically) finding the pointer to
> > struct hotplug_slot  if I have a pointer to struct pci_dev in hand.
> 
> There is no way, sorry.  Remember, multiple pci_dev can point to a
> single hotplug slot.

Right. I have I pointer to a pci_dev. I want to find the pointer to the 
hotplug slot its in.

> > I am sorely tempted to write a generic patch to
> > drivers/pci/hotplug/pci_hotplug_core.c to add this support
> > (getting it from each of the hotplug arch'es).  Should I?
> > If I submit sucha patch, would it get rejected out of hand 
> > as a bad idea?
> > 
> > I need this for the generic fallback PCI error recovery support;
> 
> Why?

I don't understand the question...

Because after discussions on the LKML, everyone decided that this
code should be written in as generic a way as possible, rather
than arch-dependent, because there will soon be a variety of PCI
chipsets that will be able to detect PCI errors. 

> > I have a pointer to the device; if its in a hotplug slot,
> > I want to toggle power to it.
> 
> No you do not.  That's a userspace policy, not something the kernel
> should do.

Argh.  I thought we've run around the table a few times on this issue
already.  It is impossible for userspace to recover from PCI errors.
The canonical example is the failure of a disk system underneath a block
device. 

All other bus errors are handled in the device drivers; for example,
scsi errors are handled by scsi drivers and/or scsi-generic code.
fiber-channel errors are handled by the fiber channel controllers.
Ethernet hangs are handled by ethernet watchdogs in each ethernet
driver.  I think its unrealistic at this point to try to turn PCI 
error recovery into a userspace policy.


--linas



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