On Thursday, November 01, 2012 03:38:19 PM Yinghai Lu wrote: > On Thu, Nov 1, 2012 at 2:21 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > >> So you are going to replace acpi_device/acpi_driver with > >> platform_device/platform_driver ? > > > > Not exactly. Let me start from the big picture, though. :-) > > > > First off, we need to unify the handling of devices by the ACPI subsystem > > regardless of whether they are on a specific bus, like PCI, or they are > > busless "platform" devices. > > > > Currently, if a device is on a specific bus *and* there is a device node in the > > ACPI namespace corresponding to it, there will be two objects based on > > struct device for it eventually, the "physical node", like struct pci_dev, and > > the "ACPI node" represented by struct acpi_device. They are associated with > > each other through the code in drivers/acpi/glue.c. In turn, if the device is > > busless and not discoverable natively, we only create the "ACPI node" struct > > acpi_device thing for it. Those ACPI nodes are then *sometimes* bind to > > drivers (represented by struct acpi_driver). > > > > The fact that the busless devices are *sometimes* handled by binding drivers > > directly to struct acpi_device while the other devices are handled through > > glue.c confuses things substantially and causes problems to happen right now > > (for example, acpi_driver drivers sometimes attempt to bind to things that have > > other native drivers and should really be handled by them). > > Furthermore, the situation will only get worse over time if we don't do > > anything about that, because we're going to see more and more devices that > > won't be discoverable natively and will have corresponding nodes in the ACPI > > namespace and we're going to see more buses whose devices will have such > > nodes. > > > > Moreover, for many of those devices there are native drivers present in > > the kernel tree already, because they will be based on IP blocks used in > > the current hardware (for example, we may see ARM-based systems based on > > exactly the same hardware with ACPI BIOSes and without them). That applies > > to busless devices as well as to devices on specific buses. > > > > Now, the problem is how the unification is going to be done and I honestly > > don't think we have much *choice* here. Namely, for PCI (and other devices > > discoverable natively) we pretty much have to do the glue.c thing (or something > > equivalent), because we need to match what we've discovered natively against > > the information from the ACPI tables in the BIOS. This means that for busless > > devices we need to create "physical" nodes as well, so that all of them are > > handled by drivers binding to the "physical" node rather than to struct > > acpi_device. This also will allow us to reuse the existing drivers with > > minimum modifications (well, hopefully). > > ok, acpi_driver will be killed at first. > > acpi_pci_root_driver will be converted to platform driver or > add acpi_pci_host_bridge to work with pci_host_bridge. Yup. > BTW, the problem for hotadd pci root bus, > the acpi_driver ops.add can pci root bus and create pci dev before all > acpi device get > created still there. > https://lkml.org/lkml/2012/10/5/569 Yes, I'm aware of that, it's on my todo list FWIW. :-) Thanks, 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
