On Wed, 2012-11-28 at 23:49 +0100, Rafael J. Wysocki wrote: > On Wednesday, November 28, 2012 03:33:27 PM Toshi Kani wrote: > > > > > > > > I think it has some challenge as well. We bind an ACPI driver with > > > > > > > > device_register(), which calls device_add()-> kobject_add(). So, all > > > > > > > > non-present ACPI device objects will show up in sysfs, unless we can > > > > > > > > change the core. This will change user interface. There can be quite > > > > > > > > many non-present devices in ACPI namespace depending on FW > > > > > > > > implementation. > > > > > > > > > > > > > > If additional devices appear in sysfs, that's not a problem. If there > > > > > > > were fewer of them, that would be a real one. :-) > > > > > > > > > > > > I see. I guess this means that once we expose all non-present devices > > > > > > in sysfs, we cannot go back to the current way. So, we need to be very > > > > > > careful. Anyway, this model requires separate handling for static ACPI > > > > > > [1] and dynamic ACPI [2], which may make the state model complicated. > > > > > > > > > > > > 1. Static ACPI - No creation / deletion of acpi_device at hot-plug. > > > > > > 2. Dynamic ACPI - Create acpi_device at hot-add, delete at hot-remove. > > > > > > > > > > Sure. The complication here is that we'll need to handle the removal of > > > > > a bunch of struct acpi_device objects when a whole table goes away. > > > > > > > > > > However, first, we don't seem to handle table unloading now. At least > > > > > acpi_unload_parent_table() is not called from anywhere as far as I can > > > > > say. Second, we'll need to handle the removal of struct acpi_device objects > > > > > _anyway_ on table unload, this way or another. > > > > > > > > AML is the one that requests loading/unloading of SSDT for dynamic ACPI. > > > > In hot-add, _Lxx method executes AML_LOAD_OP or AML_LOAD_TABLE_OP to > > > > load SSDT and then sends a notification to the OS. In hot-remove, _EJ0 > > > > method executes AML_UNLOAD_OP to unload SSDT. Of course, ACPICA does > > > > the actual work on behalf of AML. But this is not visible to ACPI core > > > > or drivers, unless it checks ACPI namespace to see if any device objects > > > > disappeared after _EJ0. > > > > > > Oh, we have a handler for that event, but we don't really use it. :-) > > > > > > And I wonder what happens to the struct acpi_device objects associated with > > > the ACPI handles in the table being unloaded? > > > > If we use an ACPI handle that does not associate with a device object, > > ACPICA returns AE_NOT_FOUND or AE_NOT_EXIST. But, we should remove > > acpi_device that does not have its associated ACPI object. Currently, > > we create acpi_device on hot-add and remove it on hot-remove, so it is > > OK. But if we start creating acpi_device objects for non-present > > devices, we need to worry about if acpi_device objects indeed have their > > associated ACPI objects. That's the complication I mentioned above. > > My question was about something different. Is it actually guaranteed > that all struct device objects associated with the given ACPI table will > be removed before that table is unloaded? Yes, it is guaranteed currently. acpi_bus_hot_remove_device() calls acpi_bus_trim(), which deletes all acpi_device objects under of the notified object. It then calls _EJ0 of the notified object, which unloads all ACPI objects under the notified object. Thanks, -Toshi -- 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
