linux-kernel - Re: [PATCH 0/4, v3] Physical PCI slot objects

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Message-ID: <474E6E82.40307@jp.fujitsu.com>
Date:	Thu, 29 Nov 2007 16:47:14 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Alex Chiang <achiang@...com>, Gary Hade <garyhade@...ibm.com>,
	Matthew Wilcox <matthew@....cx>, gregkh@...e.de,
	kristen.c.accardi@...el.com, lenb@...nel.org, rick.jones2@...com,
	linux-kernel@...r.kernel.org, linux-pci@...ey.karlin.mff.cuni.cz,
	kaneshige.kenji@...fujitsu.com,
	pcihpd-discuss@...ts.sourceforge.net, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 0/4, v3] Physical PCI slot objects

> Hi Gary, Kenji-san, et. al,
> 
> * Gary Hade <garyhade@...ibm.com>:
>> Alex, What I was trying to suggest is a boot-time kernel
>> option, not a kernel configuration option.  The basic idea is
>> to give the user (with a single binary kernel) the ability to
>> include your ACPI-PCI slot driver feature changes only when
>> they are really needed.  In addition to reducing the number of
>> system/PCI hotplug driver combinations where your changes would
>> need to be validated, I believe would also help alleviate other
>> worries (e.g. Andi Kleen's memory consumption concern).  I
>> believe this goal could also be achieved with the kernel config
>> option by making the pci_slot module runtime loadable with the
>> PCI hotplug drivers only visiting your new code when the
>> pci_slot driver is loaded, although I think this would be more
>> difficult to implement.
> 
> I have modified my patch series so that the final patch that
> introduces my ACPI-PCI slot driver is a full-fledged module, that
> has a tristate Kconfig option.
> 

Thank you for your good job.

I tested shpchp and pciehp both with and without pci_slot module. There
seems no regression from shpchp and pciehp's point of view.
(I had a little concern about the hotplug slots' name that vary depending
on whether pci_slot functionality is enabled or disabled. But, now that we
can build pci_slot driver as a kernel module, I don't think it is a big
problem).

Only the problems is that I got Call Traces with the following error
messages when pci_slot driver was loaded, and one strange slot named
'1023' was registered (other slots are fine). This is the same problem
I reported before.

    sysfs: duplicate filename '1023' can not be created
    WARNING: at fs/sysfs/dir.c:424 sysfs_add_one()

    kobject_add failed for 1023 with -EEXIST, don't try to register
    things with the same name in the same directory.

On my system, hotplug slots themselves can be added, removed and replaced
with the ohter type of I/O box. The ACPI firmware tells OS the presence of
those slots using _STA method (That is, it doesn't use 'LoadTable()' AML
operator). On the other hand, current pci_slot driver doesn't check _STA.
As a result, pci_slot driver tryied to register the invalid (non-existing)
slots. The ACPI firmware of my system returns '1023' if the invalid slot's
_SUN is evaluated. This is the cause of Call Traces mentioned above. To
fix this problem, pci_slot driver need to check _STA when scanning ACPI
Namespace.

I'm sorry for reporting this so late. I'm attaching the patch to fix the
problem. This is against 2.6.24-rc3 with your patches applied. Could you
try it?

BTW, acpiphp also seems to have the same problem...

Thanks,
Kenji Kaneshige

---
 drivers/acpi/pci_slot.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

Index: linux-2.6.24-rc3/drivers/acpi/pci_slot.c
===================================================================
--- linux-2.6.24-rc3.orig/drivers/acpi/pci_slot.c
+++ linux-2.6.24-rc3/drivers/acpi/pci_slot.c
@@ -113,10 +113,17 @@ register_slot(acpi_handle handle, u32 lv
 	int device;
 	unsigned long sun;
 	char name[KOBJ_NAME_LEN];
+	acpi_status status;
+	struct acpi_device *dummy_device;
 
 	struct pci_slot *pci_slot;
 	struct pci_bus *pci_bus = context;
 
+	/* Skip non-existing device object. */
+	status = acpi_bus_get_device(handle, &dummy_device);
+	if (ACPI_FAILURE(status))
+		return AE_OK;
+
 	if (check_slot(handle, &device, &sun))
 		return AE_OK;
 
@@ -150,12 +157,18 @@ walk_p2p_bridge(acpi_handle handle, u32 
 	acpi_status status;
 	acpi_handle dummy_handle;
 	acpi_walk_callback user_function;
+	struct acpi_device *dummy_device;
 
 	struct pci_dev *dev;
 	struct pci_bus *pci_bus;
 	struct p2p_bridge_context child_context;
 	struct p2p_bridge_context *parent_context = context;
 
+	/* Skip non-existing device object. */
+	status = acpi_bus_get_device(handle, &dummy_device);
+	if (ACPI_FAILURE(status))
+		return AE_OK;
+
 	pci_bus = parent_context->pci_bus;
 	user_function = parent_context->user_function;
 

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