Re: [PATCH V3 5/6] Avoid duplicate probe for of platform devices

On Mon, 9 Jul 2012 07:58:31 -0700, Greg KH [off-list ref] wrote:

On Mon, Jul 09, 2012 at 03:46:59AM +0000, Li Yang-R58472 wrote:

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I don't understand, why is this just showing up now?  What changed to
cause this?  Couldn't that be the real problem here?

The issue is showing up because we now probe devices twice.
Previously, we just probe devices once. But now we changed the way of pci
init which makes pci controllers should be probed earlier than other
devices.
So we have to probe pci nodes separately. Probe more than once is the
root
cause of this issue.

The pci patchset I mentioned please refer to:
http://patchwork.ozlabs.org/patch/163742/

Let me try to clarify a little bit.  The of platform bus normally
traverse the device tree to add all the devices.  The change which
caused problem is that we need to probe PCIe RC devices at a earlier
stage of initialization.

That sounds, wrong.

Yes, really really wrong; starting with terminology...

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So we added these PCIe RC devices earlier than the normal device tree
traversal process.  These PCIe RC devices will be scanned again during
the normal traversal and cause duplicated devices being added.  Our
proposal is to deal with duplicated devices automatically and make it
possible to scan the device tree multiple times for devices to be
added. 

... This isn't *probing* twice; it is *registration*.  That's cause
confusion on this thread.

Then you need to put something in your own tree scanning logic to not
try to register devices multiple times.  How about a simple flag in your
device structure instead of having to muck around in the driver core
internals?

Right.  If you're going to create the pci bus devices early, then you
need to explicitly inhibit creation of them later... but still; why do
the PCI bus devices need to be registered separately from the rest of the
devices on the simple-bus?  Why not just move *all* device registration
earlier?

Although one should seriously question the need to want to recan the bus
and register devices at different times of the boot process...

Yes; the model they're trying to use sounds wrong.

g.