linux-kernel - Re: [PATCH 0/4, v14] PCI, ACPI: Physical PCI slot objects

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Message-ID: <484F2F05.3050001@jp.fujitsu.com>
Date:	Wed, 11 Jun 2008 10:48:53 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Alex Chiang <achiang@...com>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	jbarnes@...tuousgeek.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Matthew Wilcox <matthew@....cx>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kristen.c.accardi@...el.com, greg@...ah.com, lenb@...nel.org,
	pbadari@...ibm.com, linux-pci@...r.kernel.org,
	pcihpd-discuss@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4, v14] PCI, ACPI: Physical PCI slot objects

Alex-san, Jesse-san,

> Note how we're checking get_slot_from_name. That should prevent
> your scenario (b) that you describe above.
> 
> Maybe the diff was confusing, but I am definitely not removing
> your code. I'm simply adding on top of a86161b3134465f, and not
> removing it.
>

I have to apologize. I was using v14 unintentionally on my test
environment yesterday, while I thought I was using v15.

I think v15 will prevent senario (b), though I have not tried it
yet. I'll check it again.

And I agree that Alex-san's patch go to Jesse-san's linux-next.
If I found something after that, I'll report it or send a
incremental patch. To tell the truth, I have several patches
that are waiting for Alex-san's patch to be merged to linux-next:)

>> I made a below patch to prevent (b), please take a look. And could you
>> please consider merging it to "[PATCH 2/3] Introduce pci_slot" in your
>> latest series.
> 
> Ok, now this is very confusing to me. Why is this patch so
> different from a86161b3134465f?
> 
> Are you saying the call to get_slot_from_name() is no longer
> sufficient?
> 

Though I might misunderstand something about your patch, I thought
get_slot_from_name() approach would break what your patch is trying
to do.

My understanding about your patch is as follows:

(x) If multiple hotplug drivers try to register the same slot (try
    to handle the same slot, in other words), pci_hp_register()
    returns -EBUSY.

(y) If one or more drivers try to assign the same name to multiple
    slots, pci_hp_register() returns -EEXIST.

I thought senario (x) will return -EEXIST instead of -EBUSY if we
use get_slot_from_name() approach. So I made a different patch.

In addition, regardless of whether my understanding is correct or not,
I noticed my patch I sent yesterday might be not good, because I made
it under the misunderstanding that I thought pci_hp_register() is called
even by ACPI pci slot driver...

Anyway, I'll look at your patch again after having several cups of coffee.

Thanks,
Kenji Kaneshige

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