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Date: Mon, 28 Jan 2013 19:33:28 -0700 From: Toshi Kani <toshi.kani@...com> To: "Rafael J. Wysocki" <rjw@...k.pl> Cc: ACPI Devel Maling List <linux-acpi@...r.kernel.org>, 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>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 0/4] ACPI scan handlers On Mon, 2013-01-28 at 13:58 +0100, Rafael J. Wysocki 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. That's great. I agree with you. The name of attach/detach() also clarifies the purpose of the interfaces well. Thanks, -Toshi ps. I am tied up this week and will be somewhat slow to respond... > > 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 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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