On Wednesday, November 28, 2012 02:23:23 PM Toshi Kani wrote: > On Wed, 2012-11-28 at 22:09 +0100, Rafael J. Wysocki wrote: > > On Wednesday, November 28, 2012 01:31:39 PM Toshi Kani wrote: > > > On Wed, 2012-11-28 at 19:28 +0100, Rafael J. Wysocki wrote: > > > > On Wednesday, November 28, 2012 09:54:43 AM Toshi Kani wrote: > > > > > > > > > > By using acpi_install_notify_handler(), each driver needs to walk > > > > > > > > > > through the entire ACPI namespace to find its associated ACPI devices > > > > > > > > > > and call it to register one by one. I think this is more work for > > > > > > > > > > non-ACPI drivers than defining acpi_driver. > > > > > > > > > > > > > > > > > > I'm not really sure what you mean. The drivers in question already know > > > > > > > > > what the relevant ACPI device nodes are (because they need them anyway > > > > > > > > > for other purposes), so they don't need to look for them specifically and > > > > > > > > > acpi_install_notify_handler() doesn't do any namespace walking. So what > > > > > > > > > you said above simply doesn't make sense from this viewpoint. > > > > > > > > > > > > > > > > Yes, if drivers already know the relevant ACPI devices, then walking the > > > > > > > > ACPI namespace is not necessary. I was referring the case like > > > > > > > > processor_driver.c, acpi_memhotplug.c, and container.c in my statement. > > > > > > > > > > > > > > BTW, when an ACPI device is marked as non-present, which is the case > > > > > > > before hot-add, we do not create an acpi_device object and therefore do > > > > > > > not bind it with a driver. This is why these drivers walk the ACPI > > > > > > > namespace and install their notify handlers regardless of device status. > > > > > > > > > > > > So maybe we should create struct acpi_device objects in that case too? > > > > > > > > > > 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? Rafael -- 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
