On Monday, December 23, 2013 02:58:38 PM Rafael J. Wysocki wrote: > On Saturday, December 14, 2013 06:07:06 AM Rafael J. Wysocki wrote: > > On Friday, December 13, 2013 02:17:32 PM Yasuaki Ishimatsu wrote: > > > (2013/12/13 13:56), Rafael J. Wysocki wrote: > > > > 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. > > > > > > This idea seems to same as your previous work. > > > http://lkml.org/lkml/2013/2/23/97 > > > > No, it is not. That one didn't involve physical device representations. > > > > > How about add autoremove flag into acpi_hotplug_profile and check it as follow: > > > > This is very similar to "enable" except that it generates the uevent and > > "enable" doesn't. You might as well modify "enable" to trigger a uevent if > > eject is not enabled (note that with the latest patches in linux-next "enable" > > only applies to eject). > > > > That said I don't think we should generate any uevents for struct acpi_device > > objects, because they are not devices. > > > > > --- > > > drivers/acpi/scan.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > > > index 5383c81..c43d110 100644 > > > --- a/drivers/acpi/scan.c > > > +++ b/drivers/acpi/scan.c > > > @@ -409,6 +409,11 @@ static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data) > > > ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED; > > > goto err_out; > > > } > > > + if (!handler->hotplug.autoremove) { > > > + kobject_uevent(&device->dev.kobj, KOBJ_CHANGE); > > > + ost_code = ACPI_OST_SC_EJECT_NON_SPECIFIC_FAILURE; > > > + goto err_out; > > > + } > > > acpi_evaluate_hotplug_ost(handle, ACPI_NOTIFY_EJECT_REQUEST, > > > ACPI_OST_SC_EJECT_IN_PROGRESS, NULL); > > > break; > > > > > > Adding the check into "acpi_hotplug_notify_cb()", user need not change the > > > flag for removing container device by "sysfs eject". > > > > Which is utterly confusing. There is no reason whatsoever why the sysfs eject > > attribute should work differently from the event-triggered eject. Quite the > > opposite is the case: it should work in the same way in my opinion so that it > > is possible to test the eject code path using that attribute. > > > > I'm traveling now, but when I get back home (next week), I'll try to implement > > the thing I was talking about above. > > It took some more time than I had expected, but I finally was able to get to that. > > The following two patches implement the idea. This is the minimum (in my opinion) > implementation and it may be extended in some ways. > > Patch [1/2] introduces a new demand_offline flag for struct acpi_hotplug_profile > that makes acpi_scan_hot_remove() check the offline status of the device object's > companion physical devices to start with and return -EBUSY if at least one of them > is not offline. > > Patch [2/2] uses that flag to implement the container handling. The details are > in the changelog, but that's how it is supposed to work. > > During the initial namespace scan the container ACPI scan handler should create > "physical" system container device under /sys/devices/system/container/ for > each ACPI container object (the sysfs name of that device should be the same as > the sysfs name of the corresponding container object and they should be linked > to each other via the firmware_node and physical_node symbolic links, respectively). > Those system container devices are initially online. > > When a container eject event happens, acpi_scan_hot_remove() will notice that > hotplug.demand_offline is set in the device object's scan handler and will > check the online status of its "physical" companion device, which is online > (that is the system container device the above paragraph is about). That will > cause KOBJ_CHANGE to be emitted for the system container device and -EBUSY to > be returned by acpi_scan_hot_remove(). > > Now, user space needs to offline the system container device through its online > sysfs attribute (that should be present, because the bus type for containers > provides the online and offline callbacks). However, the offline for system > container devices will only succeed if the physical devices right below the > container are all offline, so user space will have to offline those devices > before attempting to offline the system container device itself. When > finished, user space can trigger the container removal with the help of the > eject sysfs attribute of the ACPI container object pointed to by the system > container device's firmware_node link (this time the check in > acpi_scan_hot_remove() will succeed, because the system container device in > question is now offline). > > The way it is implemented is a bit hackish (the driver_data pointer is slightly > abused), but that's a special case and I wanted to avoid adding new fields to > struct device just for handling it. > > The patches haven't been tested yet. I'm going to do that later today, but > first I need to take care of some other things, so that has to wait. The series of the two patches: [1/2] ACPI / hotplug: Add demand_offline hotplug profile flag https://patchwork.kernel.org/patch/3396711/ [2/2] ACPI / hotplug / driver core: Handle containers in a special way https://patchwork.kernel.org/patch/3399081/ has been tested now and seems to work as expected, at least for a container that has no children (that's one I could simulate easily in a meaningful way). For this reason, if there are no objections, I'll resend them as an official submission during the next couple of days. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
