Re: [PATCH 0/4] ACPI scan handlers

[Yinghai Lu]

On Mon, Jan 28, 2013 at 4:58 AM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> 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.

Good, esp you move away hard code in scan.c for platform devices.

Test with pci root bus hotplug, and it works well.

So for all 4,

Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx>

It will have some merging conflicts change in drivers/acpi/internel.h
in pci/next for pci root bus hotplug support.
But it should be very simple to solve it.

Thanks

Yinghai
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