On Tuesday, November 19, 2013 06:22:07 PM Toshi Kani wrote: > On Wed, 2013-11-20 at 01:08 +0100, Rafael J. Wysocki wrote: > > On Wednesday, November 20, 2013 12:42:28 AM Rafael J. Wysocki wrote: > > > On Tuesday, November 19, 2013 02:58:40 PM Toshi Kani wrote: > > > > On Tue, 2013-11-19 at 22:10 +0100, Rafael J. Wysocki wrote: > > > > > > On Tuesday, November 19, 2013 10:48:51 AM Toshi Kani wrote: > > > > > > > On Mon, 2013-11-18 at 22:39 +0100, Rafael J. Wysocki wrote: > > > > > > > > On Monday, November 18, 2013 11:10:05 AM Toshi Kani wrote: > > > > > > > > > On Thu, 2013-11-14 at 00:16 +0100, Rafael J. Wysocki wrote: > > > > > > > > > > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > > > > > > > > > > > > > > > > > > > Since the PCI host bridge scan handler does not set > > > > > > > > > > hotplug.enabled, > > > > > > > > > > the check of it in acpi_bus_device_eject() effectively > > > > > > > > > > prevents the > > > > > > > > > > root bridge hot removal from working after commit > > > > > > > > > > a3b1b1ef78cd > > > > > > > > > > (ACPI / hotplug: Merge device hot-removal routines). > > > > > > > > > > However, that > > > > > > > > > > check is not necessary, because the other > > > > > > > > > > acpi_bus_device_eject() > > > > > > > > > > users, acpi_hotplug_notify_cb and acpi_eject_store(), do > > > > > > > > > > the same > > > > > > > > > > check by themselves before executing that function. > > > > > > > > > > > > > > > > > > > > For this reason, remove the scan handler check from > > > > > > > > > > acpi_bus_device_eject() to make PCI hot bridge hot removal > > > > > > > > > > work > > > > > > > > > > again. > > > > > > > > > > > > > > > > > > I am curious why the PCI host bridge scan handler does not set > > > > > > > > > hotplug.enabled. Is this how it disables hotplug via sysfs > > > > > > > > > eject but > > > > > > > > > enables via ACPI notification? > > > > > > > > > > > > > > > > It just doesn't register for hotplug at all. I guess it could > > > > > > > > set that > > > > > > > > bit alone, but then it would be quite confusing and the check > > > > > > > > is not > > > > > > > > necessary anyway. > > > > > > > > > > > > > > I see. Given how the PCI host bridge scan handler is integrated > > > > > > > today, > > > > > > > the change looks reasonable to me. > > > > > > > > > > > > Looking further, I noticed that there is one more issue to address. > > > > > > The > > > > > > patch below applies on top of your patchset. > > > > > > > > > > > > From: Toshi Kani <toshi.k...@hp.com> > > > > > > Subject: [PATCH] ACPI / hotplug: Fix conflicted PCI bridge notify > > > > > > handlers > > > > > > > > > > > > The PCI host bridge scan handler installs its own notify handler, > > > > > > handle_hotplug_event_root(), by itself. Nevertheless, the ACPI > > > > > > hotplug framework also installs the common notify handler, > > > > > > acpi_hotplug_notify_cb(), for PCI root bridges. This causes > > > > > > acpi_hotplug_notify_cb() to call _OST method with unsupported > > > > > > error as hotplug.enabled is not set. > > > > > > > > > > > > To address this issue, introduce hotplug.self_install flag, which > > > > > > indicates that the scan handler installs its own notify handler by > > > > > > itself. The ACPI hotplug framework does not install the common > > > > > > notify handler when this flag is set. > > > > > > > > > > Good catch! > > > > > > > > > > Still, I don't think we need a new flag, because we know that that > > > > > scan handler doesn't support hotplug, because its hotplug profile > > > > > hasn't been registered (that actually applies to all scan handlers > > > > > without hotplug support, not only the root host bridge). > > > > > > > > When a scan handler does not support hotplug at all, the common notify > > > > handler should be installed so that it can call _OST with an appropriate > > > > response. > > > > > > That creates an arbitrary difference between devices that have scan > > > handlers > > > and devices that don't have them (PCI, USB, SATA etc). So if we want _OST > > > to be called for all devices for which hotplug is not supported, that > > > should be implemented in a different way and not necessarily in 3.13. > > I do not think we have an immediate issue since it only matters when the > firmware supports ACPI hotplug with _OST. Such device types are CPU, > memory, container, and PCI bridge, which uses scan handlers. USB, SATA, > etc. do not use ACPI hotplug. That said, ideally, we should be able to > call _OST for any device types. > > > > > > Moreover, > > > > > if it does support hotplug, but the hotplug profile hasn't been > > > > > registered due to an error, we still should not install the notify > > > > > handler I think. > > > > > > > > This case, I think the common notify handler should be installed so that > > > > it can call _OST for error response as well. The question is what to do > > > > when a scan handler has its own notify handler. > > > > Actually, having considered this particular case a bit more I think that it > > is useful to install acpi_hotplug_notify_cb() for things whose scan handlers > > register hotplug support, but the registration fails (which should be > > treated > > as "permanently disabled"). > > > > However, I still think that devices whose scan handlers don't support > > hotplug > > at all should be treated consistently with devices without scan handlers. > > Basically, the kernel needs to be compliant with ACPI spec. Once the > kernel tells firmware that it supports _OST, it needs to call _OST for > an ACPI hotplug event when _OST is implemented on the object. Although > we cannot assure this behavior for the devices without scan handler, we > should do so for the devices with scan handlers. > > > So, what about the slightly modified patch below? > > Well, I do not think it is right. The kernel is supposed to tell > firmware that it does not support hotplug when it doesn't...
OK, I see your point. I'll apply your patch, then, but I'm going to rename the new flag to "ignore". Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
