Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757420AbXE1M0t (ORCPT ); Mon, 28 May 2007 08:26:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752106AbXE1M0m (ORCPT ); Mon, 28 May 2007 08:26:42 -0400 Received: from ppsw-4.csi.cam.ac.uk ([131.111.8.134]:44955 "EHLO ppsw-4.csi.cam.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbXE1M0l (ORCPT ); Mon, 28 May 2007 08:26:41 -0400 X-Cam-SpamDetails: Not scanned X-Cam-AntiVirus: No virus found X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ In-Reply-To: <1180353095.4242.57.camel@lov.localdomain> References: <200705272229.21263.rjw@sisk.pl> <20070527220412.GC22687@srcf.ucam.org> <1180304166.3131.66.camel@lov.localdomain> <200705280943.54312.rjw@sisk.pl> <20070528111554.GF18807@elf.ucw.cz> <1180351493.4242.31.camel@lov.localdomain> <6BFA837E-47D4-487F-9D71-FA83D6D865E5@cam.ac.uk> <1180353095.4242.57.camel@lov.localdomain> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Cc: Pavel Machek , "Rafael J. Wysocki" , Matthew Garrett , pm list , LKML , Nigel Cunningham , Alan Stern Content-Transfer-Encoding: 7bit From: Michael-Luke Jones Subject: Re: [RFC][PATCH -mm 3/3] PM: Disable _request_firmware before hibernation/suspend Date: Mon, 28 May 2007 13:26:37 +0100 To: Kay Sievers X-Mailer: Apple Mail (2.752.2) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2269 Lines: 53 On 28 May 2007, at 12:51, Kay Sievers wrote: > Either the whole idea of userspace firmware-loading should be > considered > as a problem impossible to do right because of its unsolvable side > effects. Or at least releasing loaded firmware should be the exception > for drivers which can be sure, that the firmware is not needed in > situations we try to work around here. I don't believe that it is impossible. What is needed is some thought, and maybe a loose spec. We need to think about safe ways of solving a simple problem: what to do when userspace is unable to respond to a kernel uevent request. We now have a timeout, whether it be handled synchronously or in the background. I don't think either solution is good enough. [RFC] Possible Plan: 1) request_firmware() should stick around unmodified but be marked __deprecated. 2) request_firmware_nowait() as it stands should probably be removed. After all, it only has 2 in-kernel users at the moment. 3) uevent interface should be notified when userspace handlers are / are not available so that events can be queued to be handled when userspace does turn up and re-register a hotplug event handler. 4) request_firmware_async() introduced: asynchronous firmware loading interface built on basis of 3, such that problems at early boot and suspend / resume are avoided. Also request_firmware_async() taught to retain firmware in memory by default such that subsequent calls do not require a call to userspace if userspace is unavailable. 6) Documentation on correct firmware loading behaviour for driver authors written, together with migration notes for existing users of request_firmware(). 7) Existing uses of request_firmware() converted. *Grumble ahead* Unfortunately, I don't properly understand the uevent interface, so some of the above may be inaccurate. This is *not* my fault as there is no decent documentation (and btw, telling me to write the documentation is not the answer to that problem). Michael-Luke - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/