creating PCI-related sysfs entries

[linas]

On Tue, Jan 31, 2006 at 12:34:56PM -0800, Greg KH was heard to remark:
> On Tue, Jan 31, 2006 at 02:22:14PM -0600, linas wrote:
> > 
> > I want to create some sysfs entries in order to report on the 
> > status of PCI slots.  (If you are guessing that this pertains
> > to the PCI error recovery code, you'd be right).  I'm having 
> > trouble figuring out the best way to do this.
> > 
> > There are existing entries at /sys/bus/pci/slots/... but these
> > are for hotplug slots only; none of the soldered-onto-the-MB
> > devices show up here.  Is this intentional, or is this a bug/
> > overshight/not-yet-implemented thing?
> 
> Not implemented, as it's up to a pci hotplug controller driver to
> provide those slots.  It sounds like your driver needs to be expanded :)

Hmm. But these slots are not hot-plugabble; should the arch
use the hotplug infrastructure even on those slots?

I note that /sys/devices/pciXXXX does have all of the pci 
slos listed, so perhaps that is where I can place per-slot data.

> > I also want to report some roll-up system-wide statistics
> > both /sys/module and /sys/class seem reasonable. My code
> > does not compile as a module. Suggestions?
> 
> What kind of statistics?  Is this driver related?  PCI bus related?
> Device related?

Related to the PCI error recovery. I'm not sure how to conceptually
peg this: one could say that it is the driver for a specific type
of pci-host bridge, although the code is not currently structured 
as such. Should I try to restructure it as such? If so, I'm not 
clear on how to proceed; I can't say I've clearly seen a kernel
abstraction of a pci-host bridge device onto which to staple myself.

I wanted to report a few read-only statistics, and a few writeable 
parameters:

Read-only:
-- total number of PCI device resets due to detected errors
-- total number of "false positives" (probable errors that weren't)
-- some other misc related stats.

Most, but not all, of these statistics could be obtained by 
totalling up the per-slot statistics.

Writable: 
-- Number of reset tries to perform before concluding that the 
   device is hopelessly dead.  Resets are disruptive and intensive,
   and I don't want to get stuck in an inf loop on a dead device.


Linas.