Message-ID: <4311642.nDd2RCVeDc@vostro.rjw.lan>
Date:	Mon, 28 Jan 2013 13:58:35 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>,
	Toshi Kani <toshi.kani@...com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 0/4] ACPI scan handlers

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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