On Fri, Dec 27, 2013 at 11:28:34PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > ACPI container devices require special hotplug handling, at least > on some systems, since generally user space needs to carry out > system-specific cleanup before it makes sense to offline devices in > the container. However, the current ACPI hotplug code for containers > first attempts to offline devices in the container and only then it > notifies user space of the container offline. > > Moreover, after commit 202317a573b2 (ACPI / scan: Add acpi_device > objects for all device nodes in the namespace), ACPI device objects > representing containers are present as long as the ACPI namespace > nodes corresponding to them are present, which may be forever, even > if the container devices are physically detached from the system (the > return values of the corresponding _STA methods change in those > cases, but generally the namespace nodes themselves are still there). > Thus it is useful to introduce entities representing containers that > will go away during container hot-unplug. > > The goal of this change is to address both the above issues. > > The idea is to create a "companion" container system device for each > of the ACPI container device objects during the initial namespace > scan or on a hotplug event making the container present. That system > device will be unregistered on container removal. A new bus type > for container devices is added for this purpose, because device > offline and online operations need to be defined for them. The > online operation is a trivial function that is always successful > and the offline uses a callback pointed to by the container device's > offline member. > > For ACPI containers that callback simply walks the list of ACPI > device objects right below the container object (its children) and > checks if all of their physical companion devices are offline. If > that's not the case, it returns -EBUSY and the container system > device cannot be put offline. Consequently, to put the container > system device offline, it is necessary to put all of the physical > devices depending on its ACPI companion object offline beforehand. > > Container system devices created for ACPI container objects are > initially online. They are created by the container ACPI scan > handler whose hotplug.demand_offline flag is set. That causes > acpi_scan_hot_remove() to check if the companion container system > device is offline before attempting to remove an ACPI container or > any devices below it. If the check fails, a KOBJ_CHANGE uevent is > emitted for the container system device in question and user space > is expected to offline all devices below the container and the > container itself in response to it. Then, user space can finalize > the removal of the container with the help of its ACPI device > object's eject attribute in sysfs. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > Tested-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
