From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753183Ab2KSWbd (ORCPT ); Mon, 19 Nov 2012 17:31:33 -0500 Received: from mail-da0-f46.google.com ([209.85.210.46]:49896 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752034Ab2KSWba (ORCPT ); Mon, 19 Nov 2012 17:31:30 -0500 Date: Mon, 19 Nov 2012 14:32:21 -0800 From: Greg Kroah-Hartman To: "Rafael J. Wysocki" Cc: Mika Westerberg , Bjorn Helgaas , Jean Delvare , ben-linux@fluff.org, w.sang@pengutronix.de, linux-kernel@vger.kernel.org, lenb@kernel.org, rafael.j.wysocki@intel.com, broonie@opensource.wolfsonmicro.com, grant.likely@secretlab.ca, linus.walleij@linaro.org, mathias.nyman@linux.intel.com, linux-acpi@vger.kernel.org Subject: Re: [PATCH 2/2] ACPI / platform: Initialize ACPI handles of platform devices in advance Message-ID: <20121119223221.GB2250@kroah.com> References: <1352977397-2280-1-git-send-email-mika.westerberg@linux.intel.com> <1855340.enMgVW1AIC@vostro.rjw.lan> <12675091.beenkZth4X@vostro.rjw.lan> <1610515.dOb8aMkzLk@vostro.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1610515.dOb8aMkzLk@vostro.rjw.lan> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 19, 2012 at 09:44:21PM +0100, Rafael J. Wysocki wrote: > On Monday, November 19, 2012 06:45:22 PM Rafael J. Wysocki wrote: > > On Monday, November 19, 2012 06:32:06 PM Rafael J. Wysocki wrote: > > > On Monday, November 19, 2012 08:23:34 AM Greg Kroah-Hartman wrote: > > > > On Sun, Nov 18, 2012 at 10:13:59PM +0100, Rafael J. Wysocki wrote: > > > > > From: Rafael J. Wysocki > > > > > > > > > > The current platform device creation and registration code in > > > > > acpi_create_platform_device() is quite convoluted. This function > > > > > takes an ACPI device node as an argument and eventually calls > > > > > platform_device_register_resndata() to create and register a > > > > > platform device object on the basis of the information contained > > > > > in that code. However, it doesn't associate the new platform > > > > > device with the ACPI node directly, but instead it relies on > > > > > acpi_platform_notify(), called from within device_add(), to find > > > > > that ACPI node again with the help of acpi_platform_find_device() > > > > > and acpi_platform_match() and then attach the new platform device > > > > > to it. This causes an additional ACPI namespace walk to happen and > > > > > is clearly suboptimal. > > > > > > > > > > Use the observation that it is now possible to initialize the ACPI > > > > > handle of a device before calling device_add() for it to make this > > > > > code more straightforward. Namely, add a new field to struct > > > > > platform_device_info allowing us to pass the ACPI handle of interest > > > > > to platform_device_register_full(), which will then use it to > > > > > initialize the new device's ACPI handle before registering it. > > > > > This will cause acpi_platform_notify() to use the ACPI handle from > > > > > the device structure directly instead of using the .find_device() > > > > > routine provided by the device's bus type. In consequence, > > > > > acpi_platform_bus, acpi_platform_find_device(), and > > > > > acpi_platform_match() are not necessary any more, so remove them. > > > > > > > > Why can't you use the platform_data * that is already in struct device > > > > for this, instead of adding an acpi-specific field to the > > > > platform_device structure? > > > > > > Hmm, I kind of don't understand the question. :-) > > > > > > Yes, we have acpi_handle in struct device (it actually is being added by a > > > patch you've acked) and we use it. The whole point here is to streamline > > > of the initalization of that field. > > > > > > > If not that, surely there is another field in struct device that you > > > > could use that is free for this type of device? > > > > > > Yes, there is one and as I said above. :-) > > > > > > I'd be happy to use the struct device's field directly, but > > > platform_device_register_full() allocates memory for the struct device in > > > question, so that field actually doesn't exist yet when it is called. > > > > > > > > struct platform_device_info { > > > > > struct device *parent; > > > > > + void *acpi_handle; > > > > > > > > Oh, and if I do accept this, I want a "real" structure pointer here > > > > please, not a void * "handle". That way is a slippery slope to the > > > > Windows kernel programming style :) > > > > > > This is (void *), because the field being initialized is (void *). That field, > > > in turn, is (void *), because ACPICA defines it that way. I thought about > > > wrapping that in some more meaningless data type, but I did't find a way > > > > s/meaningless/meaningful/ > > Well, perhaps I'll describe the problem to you, maybe you can help. :-) > > So, we want to have acpi_handle (or acpi_node) in addition to of_node in struct > device (to be used in the analogous way plus for the execution of AML methods), > but we don't want all users of device.h to have to include ACPI headers > where the acpi_handle data type is defined. For this reason, we're using > (void *) as its data type now, which let's say I'm not really happy with. > > I've been thinking about that for quite a while, though, and I'm not really > sure what to do about that. Perhaps we could define something like > > struct acpi_dev_node { > #ifdef CONFIG_ACPI > void *handle; > #endif > }; > > in device.h and use that as "struct acpi_dev_node acpi_node;" in struct device. > Then, we could add the following macro > > #ifdef CONFIG_ACPI > #define ACPI_HANDLE(dev) ((dev)->acpi_node.handle) > #else > #define ACPI_HANDLE(dev) (NULL) > #endif > > and redefine DEVICE_ACPI_HANDLE(dev) as ((acpi_handle)ACPI_HANDLE(dev)). > > Then, the $subject patch would add "struct acpi_dev_node acpi_node;" to > struct platform_device_info and use ACPI_HANDLE(dev) instead of accessing > the struct device's field directly. > > I wonder what you think? I like the hack of using an empty structure here, that's fine with me, and makes me feel a little bit better about the whole "void *" stuff. If you respin the patch with this, I'll ack it. thanks, greg k-h