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

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Date:	Wed, 11 Jun 2008 15:29:51 +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,

Alex Chiang wrote:
> Hi Kenji-san,
> 
> * Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>:
>> 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.
> 
> You can check either v15, which applies to Stephen Rothwell's
> linux-next, or you can check v16, which applies to Jesse's
> linux-next.
> 
> The only difference is in patch 1/3, where we are touching
> fakephp, which is not the patch that is confusing us here. :)
> 
>> 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:)
> 
> Yeah, I think incremental patches from here out are good.
> 
>>>> 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.
> 
> That was the original intent, but I think that returning -EEXIST
> for (x) should be sufficient. If it turns out we really do want
> -EBUSY for (x), we can add your latest fixup patch later.
>

Ok, I understood. Thank you for clarification. I also think your
latest patch is sufficient.

Just in case, I would like to tell you the fact that (x) has following
two cases, though I think you already recognized about it.

  (x-1) If multiple hotplug drivers try to handle the same slot with
        different names, pci_hp_register() returns -EBUSY.

  (x-2) If multiple hotplug drivers try to handle the same slot with
        the same name, pci_hp_register() returns -EEXIST.

Thanks,
Kenji Kaneshige

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