From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753435AbaJ1UEc (ORCPT ); Tue, 28 Oct 2014 16:04:32 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:32835 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753191AbaJ1UEa (ORCPT ); Tue, 28 Oct 2014 16:04:30 -0400 Date: Tue, 28 Oct 2014 13:04:24 -0700 From: Guenter Roeck To: Pavel Machek Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Alan Cox , Alexander Graf , Andrew Morton , Geert Uytterhoeven , Heiko Stuebner , Lee Jones , Len Brown , Philippe =?iso-8859-1?Q?R=E9tornaz?= , "Rafael J. Wysocki" , Romain Perier Subject: Re: [PATCH v4] kernel: Add support for power-off handler call chain Message-ID: <20141028200424.GA20617@roeck-us.net> References: <1414516266-4965-1-git-send-email-linux@roeck-us.net> <20141028182312.GA13636@amd> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141028182312.GA13636@amd> User-Agent: Mutt/1.5.21 (2010-09-15) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A02020A.544FF6CE.00AF,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.000 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 2 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 28, 2014 at 07:23:12PM +0100, Pavel Machek wrote: > On Tue 2014-10-28 10:11:06, Guenter Roeck wrote: > > Various drivers implement architecture and/or device specific means to > > power off the system. For the most part, those drivers set the global > > variable pm_power_off to point to a function within the driver. > > > > This mechanism has a number of drawbacks. Typically only one scheme > > to remove power is supported (at least if pm_power_off is used). > > At least in theory there can be multiple means remove power, some of > > which may be less desirable. For example, some mechanisms may only > > power off the CPU or the CPU card, while another may power off the > > entire system. Others may really just execute a restart sequence > > or drop into the ROM monitor. Using pm_power_off can also be racy > > if the function pointer is set from a driver built as module, as the > > driver may be in the process of being unloaded when pm_power_off is > > called. If there are multiple power-off handlers in the system, removing > > a module with such a handler may inadvertently reset the pointer to > > pm_power_off to NULL, leaving the system with no means to remove power. > > > > Introduce a system power-off handler call chain to solve the described > > problems. This call chain is expected to be executed from the architecture > > specific machine_power_off() function. Drivers and architeceture code > > providing system power-off functionality are expected to register with > > this call chain. When registering a power-off handler, callers can > > provide a priority to control power-off handler execution sequence > > and thus ensure that the power-off handler with the optimal capabilities > > to remove power for a given system is called first. > > > > Cc: Alan Cox > > Cc: Alexander Graf > > Cc: Andrew Morton > > Cc: Geert Uytterhoeven > > cc: Heiko Stuebner > > Cc: Lee Jones > > Cc: Len Brown > > Acked-by: Pavel Machek > Thanks! Guenter