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SubjectRe: [PATCH 7/10] ACPI / hotplug: Move container-specific code out of the core
Hi Rafael,

Please share your more detailed idea. I started to implement the following
idea. But the idea has one problem.

>>> The eject work flow can be:
>>> (1) an eject event occurs,
>>> (2) the container "physical" device fails offline in acpi_scan_hot_remove()
>>> emmitting, say, KOBJ_CHANGE for the "physical" device,
>>> (3) user space notices the KOBJ_CHANGE and does the cleanup as needed,
>>> (4) user space changes the "physical" container device flag controlling
>>> offline to 0,
>>> (5) user space uses the sysfs "eject" attribute of the ACPI container object
>>> to finally eject the container,
>>> (6) the offline in acpi_scan_hot_remove() is now successful, because the
>>> flag controlling it has been set to 0 in step (4),
>>> (7) the "physical" container device goes away before executing _EJ0,
>>> (8) the container is ejected.

I want to emit KOBJ_CHANGE before offlining devices on container device at (2).
But acpi_scan_hot_remove() offlines devices on container device at first.
So when offline container device, devices on container has been offlined.

Thus the idea cannot fulfill my necessary feature.

Yasauaki Ishimatsu

Yasauaki Ishimatsu

>>> Of course, if the flag controlling container offline is 0 to start with, step
>>> (6) will now occur directly after (1), so whoever wants containers to be
>>> hot-removed automatically may just clear that flag for all of them on boot.
>>> How does that sound?
>> The above ideas are almost O.K. I want kernel to notify user space of KOBJ_OFFLINE.
>> Even if user space catches "KOBJ_CHANGE", user doesn't know whether the notification
>> is offline or not.
> It is easy to figure out, though. Since the KOBJ_CHANGE will be emitted for
> container devices only in that situation, user space can see that (1) it is
> from a container and (2) it is KOBJ_CHANGE, so it must mean "container offline
> has been attempted".
> My concern with using KOBJ_OFFLINE for that is that device_offline() emits it
> too on success and it may be easily confused with the one emitted on failure
> for containers.
> Thanks,
> Rafael

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