On Mon, Dec 17, 2012 at 4:20 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > The ACPI handles of PCI root bridges need to be known to > acpi_bind_one(), so that it can create the appropriate > "firmware_node" and "physical_node0" files for them, but currently > the way it gets to know those handles is not exactly straightforward > (to put it lightly). > > This is how it works, roughly: > > 1. acpi_bus_scan() finds the handle of a PCI root bridge, > creates a struct acpi_device object for it and passes that > object to acpi_pci_root_add(). > > 2. acpi_pci_root_add() creates a struct acpi_pci_root object, > populates its "device" field with its argument's address > (device->handle is the ACPI handle found in step 1). > > 3. The struct acpi_pci_root object created in step 2 is passed > to pci_acpi_scan_root() and used to get resources that are > passed to pci_create_root_bus(). > > 4. pci_create_root_bus() creates a struct pci_host_bridge object > and passes its "dev" member to device_register(). > > 5. platform_notify(), which for systems with ACPI is set to > acpi_platform_notify(), is called. > > So far, so good. Now it starts to be "interesting". > > 6. acpi_find_bridge_device() is used to find the ACPI handle of > the given device (which is the PCI root bridge) and executes > acpi_pci_find_root_bridge(), among other things, for the > given device object. > > 7. acpi_pci_find_root_bridge() uses the name (sic!) of the given > device object to extract the segment and bus numbers of the PCI > root bridge and passes them to acpi_get_pci_rootbridge_handle(). > > 8. acpi_get_pci_rootbridge_handle() browses the list of ACPI PCI > root bridges and finds the one that matches the given segment > and bus numbers. Its handle is then used to initialize the > ACPI handle of the PCI root bridge's device object by > acpi_bind_one(). However, this is *exactly* the ACPI handle we > started with in step 1. > > Needless to say, this is quite embarassing, but it may be avoided > thanks to commit f3fd0c8 (ACPI: Allow ACPI handles of devices to be > initialized in advance), which makes it possible to initialize the > ACPI handle of a device before passing it to device_register(). > Namely, if pci_acpi_scan_root() could easily pass the root bridge's > ACPI handle to pci_create_root_bus(), the latter could set the ACPI > handle in its struct pci_host_bridge object's "dev" member before > passing it to device_register() and steps 6-8 above wouldn't be > necessary any more. > > To make that happen I decided to repurpose the 4th argument of > pci_create_root_bus(), because that allowed me to avoid defining > additional callbacks or similar things and didn't seem to impact > architectures without ACPI substantially. > > All architectures using pci_create_root_bus() directly are updated > as needed, but only x86 and ia64 are affected as far as the behavior > is concerned (no one else uses ACPI). There should be no changes in > behavior resulting from this on the other architectures. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx> and the ones in your acpi_scan_temp branches. Thanks a lot. Yinghai -- 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
