From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH 0/4] ACPI scan handlers Date: Wed, 30 Jan 2013 14:36:22 +0100 Message-ID: <2835860.8PoYodXXnK@vostro.rjw.lan> References: <1873429.MS5RQDxTye@vostro.rjw.lan> <4311642.nDd2RCVeDc@vostro.rjw.lan> <1359511110.15120.77.camel@misato.fc.hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7Bit Return-path: Received: from hydra.sisk.pl ([212.160.235.94]:32907 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754387Ab3A3NaM (ORCPT ); Wed, 30 Jan 2013 08:30:12 -0500 In-Reply-To: <1359511110.15120.77.camel@misato.fc.hp.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Toshi Kani Cc: ACPI Devel Maling List , Greg Kroah-Hartman , Bjorn Helgaas , Mika Westerberg , Matthew Garrett , Yinghai Lu , Jiang Liu , LKML On Tuesday, January 29, 2013 06:58:30 PM Toshi Kani wrote: > 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. > > > > 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. > > For the series: > > Acked-by: Toshi Kani Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.