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SubjectRe: [PATCH 7/10] ACPI / hotplug: Move container-specific code out of the core
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On Friday, December 13, 2013 11:56:32 AM Yasuaki Ishimatsu wrote:
> Hi Rafael,

Hi,

> 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.

Well, in that case we need to treat containers in a special way at the ACPI
level. Which is a bit unfortunate so to speak.

To that end I'd try to add a new flag to struct acpi_hotplug_profile, say
.verify_offline, such that if set, it would cause acpi_scan_hot_remove() to
check if all of the "physical" companions of the top-level device are offline
to start with, and if not, it would just emit KOBJ_CHANGE for the companions
that are not offline and bail out.

So the above algorithm would become:

(1) an eject event occurs,
(2) acpi_scan_hot_remove() checks the verify_offline flag in the target device's
scan_handler structure,
(3) if set (it would always be set for containers), acpi_scan_hot_remove()
checks the status of the target device's "physical" companions; if at least
one of them is offline, KOBJ_CHANGE is emitted for that "physical" device,
and acpi_scan_hot_remove() returns, [I guess we can just emit KOBJ_CHANGE
for the first companion that is not offline at this point.]
(4) user space notices the KOBJ_CHANGE and does the cleanup as needed; in the
process it carries out the offline operation for the container's "physical"
companion (there's only one such companion for each container), [That
operation for the container itself is trivial, but to succeed it requires
all devices below the container to be taken offline in advance.]
(5) user space uses the sysfs "eject" attribute of the ACPI container object
to finally eject the container,
(6) acpi_scan_hot_remove() is now successful, because the container's "physical"
companion is now offline,
(7) the "physical" container device goes away before executing _EJ0,
(8) the container is ejected.

I think that should work for you.

Thanks,
Rafael



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