On Thursday, January 24, 2013 01:26:56 AM Rafael J. Wysocki wrote:
> Hi All,
>
> There is a considerable amount of confusion in the ACPI subsystem about what
> ACPI drivers are used for. Namely, some of them are used as "normal" device
> drivers that bind to devices and handle them using ACPI control methods (like
> the fan or battery drivers), but some of them are just used for handling
> namespace events, such as the creation or removal of device nodes (I guess it
> would be fair to call that an abuse of the driver core). These two roles are
> quite distinct, which is particularly visible from the confusion about the
> role
> of the .remove() callback.
>
> For the "normal" drivers this callback is simply used to handle situations in
> which the driver needs to be unbound from the device, because one of them
> (either the device or the driver) is going away. That operation can't really
> fail, it just needs to do the necessary cleanup.
>
> However, for the namespace events handling "drivers" .remove() means that not
> only the device node in question, but generally also the whole subtree below
> it
> needs to be prepared for removal, which may involve deleting multiple device
> objects belonging to different bus types and so on and which very well may
> fail
> (for example, those devices may be used for such things like swap or they may
> be
> memory banks used by the kernel and it may not be safe to remove them at the
> moment etc.). Moreover, for these things the removal of the "driver" doesn't
> really make sense, because it has to be there to handle the namespace events
> it
> is designed to handle or else things will go remarkably awry in some places.
>
> To resolve all that mess I'd like to do the following, which in part is
> inspired
> by the recent Toshi Kani's hotplug framework proposal and in part is based on
> some discussions I had with Bjorn and others (the code references made below
> are
> based on the current contens of linux-pm.git/linux-next).
>
> 1) Introduce a special data type for "ACPI namespace event handlers" like:
>
> struct acpi_scan_handler {
> const struct acpi_device_id *ids;
> struct list_head list_node;
> int (*attach)(struct acpi_device *adev);
> int (*untie)(struct acpi_device *adev);
> int (*reclaim)(struct acpi_device *adev);
> void (*detach)(struct acpi_device *adev);
> };
After some reconsideration I think that the "untie" and "reclaim" things won't
be really useful at this level. This means that I only need ACPI scan handlers
to do .attach() and .detach() and all of that becomes really simple, so I don't
see reason to wait with that change.
The following patches introduce ACPI scan handlers and make some use of them.
[1/4] Introduce struct acpi_scan_handler for configuration tasks depending on
device IDs.
[2/4] Make ACPI PCI root driver use struct acpi_scan_handler.
[3/4] Make ACPI PCI IRQ link driver use struct acpi_scan_handler.
[4/4] Use struct acpi_scan_handler for creating platform devices enumerated via
ACPI.
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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