Re: [PATCH 0/4, v3] Physical PCI slot objects
From: Kenji Kaneshige
Date: Wed Mar 12 2008 - 08:37:24 EST
Hi Kristen,
Hello - back to this mail for a moment. I wanted to talk about acpiphp
again. You say that acpiphp has this same problem as Alex's driver wrt
evalating _SUN on a non existant object. If we skip registering the
slot in acpiphp's register_slot function if it returns 0 for _STA, we
will not detect any hotplug slots, since leaf nodes will return 0 for
_STA if a device is not present. Should we only skip it if it's parent
is a p2p bridge that has _EJ0 and the parent's _STA says empty?
I've been not looking at acpiphp code for a long time. So I need refresh
my memory before answering. Sorry.
But I want to say one thing. We can detect all the hotplug slots if ACPI
firmware doesn't provide _STA. We don't need _STA for PCI hotplug slots
and should not provide _STA for PCI hotplug slots if the system is based
on ACPI2.0 or later, because those are _ADR based devices (PCI root bridge,
which is _HID based device, is a exception). For _ADR based devices, we
should check the presence of the device using PCI bus drivers instead of
evaluating _STA. Please see the section of "_EJx (Eject)" in ACPI2.0b or
later spec. It says "For _HID devices, OSPM evaluates the _STA method. For
_ADR devices, OSPM checks with the bus driver for that device.".
BTW, acpiphp_glue.c says _STA is "optionally". I don't know what it means.
Thanks,
Kenji Kaneshige
Kristen Carlson Accardi wrote:
On Thu, 29 Nov 2007 16:47:14 +0900
Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx> wrote:
Hi Gary, Kenji-san, et. al,
* Gary Hade <garyhade@xxxxxxxxxx>:
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
Hello - back to this mail for a moment. I wanted to talk about acpiphp
again. You say that acpiphp has this same problem as Alex's driver wrt
evalating _SUN on a non existant object. If we skip registering the
slot in acpiphp's register_slot function if it returns 0 for _STA, we
will not detect any hotplug slots, since leaf nodes will return 0 for
_STA if a device is not present. Should we only skip it if it's parent
is a p2p bridge that has _EJ0 and the parent's _STA says empty?
Your input is appreciated,
Kristen
---
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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