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Message-ID: <50F2CF18.1010301@gmail.com> Date: Sun, 13 Jan 2013 23:13:28 +0800 From: Jiang Liu <liuj97@...il.com> To: "Rafael J. Wysocki" <rjw@...k.pl> CC: Bjorn Helgaas <bhelgaas@...gle.com>, Jiang Liu <jiang.liu@...wei.com>, Yijing Wang <wangyijing@...wei.com>, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org Subject: Re: [PATCH v3 4/6] PCI/acpiphp: update ACPI hotplug slot information when PCI hotplug happens On 01/10/2013 04:23 AM, Rafael J. Wysocki wrote: > On Thursday, January 10, 2013 12:29:55 AM Jiang Liu wrote: >> On 01/09/2013 08:04 AM, Rafael J. Wysocki wrote: >>> On Wednesday, January 09, 2013 12:52:23 AM Jiang Liu wrote: >>>> Currently the acpiphp driver fails to update hotplug slot information under >>>> several conditions, such as: >>>> 1) The bridge device is removed through /sys/bus/pci/devices/.../remove >>>> 2) The bridge device is added/removed by PCI hotplug driver other than the >>>> acpiphp driver itself. For example, if an IO expansion box with ACPI >>>> hotplug slots available is hot-added by the pciehp driver, all ACPI >>>> hotplug slots won't be discovered by the acpiphp driver. >>>> >>>> So hook the BUS_NOTIFY_ADD_DEVICE/BUS_NOTIFY_DEL_DEVICE events to >>>> update ACPI hotplug slot information when PCI hotplug event happens. >>>> >>>> Signed-off-by: Jiang Liu <jiang.liu@...wei.com> >>>> Signed-off-by: Yijing Wang <wangyijing@...wei.com> >>>> --- >>>> drivers/pci/hotplug/acpiphp_glue.c | 62 ++++++++++++++++++++++++++++++++++-- >>>> 1 file changed, 60 insertions(+), 2 deletions(-) >>>> >> snip >>>> +static struct notifier_block acpi_pci_hp_notifier = { >>>> + .notifier_call = &acpi_pci_hp_notify_fn, >>>> +}; >>>> + >>>> static struct acpi_pci_driver acpi_pci_hp_driver = { >>>> .add = add_bridge, >>>> .remove = remove_bridge, >>>> @@ -1448,6 +1503,8 @@ int __init acpiphp_glue_init(void) >>>> else >>>> acpi_pci_register_driver(&acpi_pci_hp_driver); >>>> >>>> + bus_register_notifier(&pci_bus_type, &acpi_pci_hp_notifier); >>> >>> Your previous patch adds a PCI bus notifier for a similar thing. Why are >>> you adding another one here? >> Hi Rafael, >> The acpiphp driver could be built as a module, and this bus notifier >> is used to setup/tear down ACPI based PCI hotplug controllers under a PCI bridge. >> The previous patch is to add/remove PCI slots. The PCI slot and PCI hotplug >> controller are related but different objects, so we use two notifiers to support >> them all. > > I would be much happier if those notifiers were not needed. At least, I'm not > sure why they need to be invoked by the driver core during device registration. > > In my opinion it would be much better if they were called only for the devices > that might need them instead of all PCI devices. > Hi Rafael, The whole thing seems a little complex, and I will try my best to explain about it:) Essentially a PCI slot is associated with a PCI bus, and a PCI bus is associated with a host bridge or P2P bridge. When hot-adding/hot-removing a PCI bus, we need to create/destroy PCI slots associated with it. So the pci_slot and acpiphp drivers need to be notified when hot-adding/hot-removing a PCI bus. But there's no common mechanism to get notified when PCI buses are being hot-added/hot-removed. So my first implementation has introduced a dedicated notifier chain for PCI bus addition/removal. Later with ongoing changes to the PCI core, I found we could rely on the existing bus notification mechanism too, so that becomes the current implementation. I have a proposal to unify the process for boot time and hotplug as below: 1) Change pci_slot and acpiphp as built-in instead of modules. 2) Get rid of acpi_pci_driver for pci_slot and acpiphp driver. 3) Register some forms of callbacks to create/destroy hotplug controllers/slots when creating/destroying PCI buses. 3.a) Rely on the bus notification mechanism to invoke callbacks. This solution is simple, but with a little overhead 3.b) Introduce a dedicated notifier chain for PCI bus hot-adding/hot-removing. This solution could get rid of the overhead, but with more code changes. 3.c) Invoke callbacks from acpi_bus_type->setup/cleanup. This solution could only support ACPI based slots, such as pci_slot and acpiphp. Any recommendations? Regards! Gerry > Thanks, > Rafael > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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