linux-kernel - Re: post 2.6.26 requires pciehp_slot_with

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Message-ID: <20080725044234.GA18511@ldl.fc.hp.com>
Date:	Thu, 24 Jul 2008 22:42:34 -0600
From:	Alex Chiang <achiang@...com>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Pierre Ossman <drzeus-list@...eus.cx>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org
Subject: Re: post 2.6.26 requires pciehp_slot_with_bus

* Matthew Wilcox <matthew@....cx>:
> On Fri, Jul 25, 2008 at 01:29:16AM +0200, Pierre Ossman wrote:
> > On Thu, 24 Jul 2008 17:08:27 -0600
> > Alex Chiang <achiang@...com> wrote:
> > 
> > > Sorry for one more round-trip, but could you turn on debugging
> > > for pciehp as well?
> > > 
> > 
> > Same thing, with debugging:
> 
> I have a laptop with a similar problem (though I don't have pciehp
> enabled, so I didn't notice it).  Obviously, we need to fix this.
> 
> There is no question in my mind that firmware has programmed the slot
> numbers incorrectly.  Here's the evidence from lspci -vvv:
> 
> 00:1c.0 PCI bridge: Intel Corporation 82801H (ICH8 Family) PCI Express Port 1 (rev 03)
>         Capabilities: [40] Express (v1) Root Port (Slot+), MSI 00
>                 SltCap: AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug+ Surpise+
>                         Slot #  2, PowerLimit 6.500000; Interlock- NoCompl-
> 00:1c.4 PCI bridge: Intel Corporation 82801H (ICH8 Family) PCI Express Port 5 (rev 03)
>         Capabilities: [40] Express (v1) Root Port (Slot+), MSI 00
>                 SltCap: AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug+ Surpise+
>                         Slot #  2, PowerLimit 6.500000; Interlock- NoCompl-
> 
> I don't think anyone can credibly argue that this is correct.  They're
> both PCIe devices, they're both both indicating that they have a slot
> (maybe if I get my screwdriver out, I can see if there's really a slot
> ...), they're on the same bus (so I don't know how the with_bus
> parameter makes any difference).
> 
> I've always hated that with_bus parameter.  I don't like it being a
> parameter and I don't like the names it produces.
> 
> Part of the problem is the kobject API.  It really hates you trying to
> register a duplicate name and won't just return -EEXIST and let you try
> a new name.  Instead it prints an ugly warning and dumps stack.  See
> kobject_add_internal() in lib/kobject.c.

Yeah, I don't really like that part of the kobject API either.

> So we need a way to find if there's already a slot of this name.  I
> don't see a kobject routine to do that.  Maybe we can do it internally
> to the pci slot code.

Well, we have this code in pci_hp_register:

        /* Check if we have already registered a slot with the same name. */
        if (get_slot_from_name(slot->name))
                return -EEXIST;

> Then we need to pick a new name for the kobject if it does collide.
> My suggestion is that the second time we find an object named "2", we
> call it "2dup1" (the third time "2dup2", etc.)  Other opinions I've
> seen include "2a", "2b", ... or "2-1", "2-2", ... or "2-brokenfw1",
> "2-brokenfw2".
> 
> I'm at OLS this week, so no patch from me.

It should be pretty easy for pci_hp_register() to fix up the name
in the event of a collision.

The hard part is figuring out a convention that we can all agree
on. ;) I've no strong feelings here, but of the options
presented, I lean towards "2a", "2b" or "2-1", "2-2".

/ac

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