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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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