From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko =?ISO-8859-1?Q?St=FCbner?= Subject: Re: [PATCH v4] kernel: Add support for power-off handler call chain Date: Tue, 28 Oct 2014 21:58:53 +0100 Message-ID: <5361222.IVraj5jbi5@diego> References: <1414516266-4965-1-git-send-email-linux@roeck-us.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from gloria.sntech.de ([95.129.55.99]:39575 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750857AbaJ1Uzn convert rfc822-to-8bit (ORCPT ); Tue, 28 Oct 2014 16:55:43 -0400 In-Reply-To: <1414516266-4965-1-git-send-email-linux@roeck-us.net> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Guenter Roeck Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Alan Cox , Alexander Graf , Andrew Morton , Geert Uytterhoeven , Lee Jones , Len Brown , Pavel Machek , Philippe =?ISO-8859-1?Q?R=E9tornaz?= , "Rafael J. Wysocki" , Romain Perier Am Dienstag, 28. Oktober 2014, 10:11:06 schrieb Guenter Roeck: > Various drivers implement architecture and/or device specific means t= o > power off the system. For the most part, those drivers set the globa= l > variable pm_power_off to point to a function within the driver. >=20 > 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, remov= ing > 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 powe= r. >=20 > Introduce a system power-off handler call chain to solve the describe= d > problems. This call chain is expected to be executed from the archit= ecture > specific machine_power_off() function. Drivers and architeceture cod= e > providing system power-off functionality are expected to register wit= h > 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 capabilit= ies > to remove power for a given system is called first. >=20 > Cc: Alan Cox > Cc: Alexander Graf > Cc: Andrew Morton > Cc: Geert Uytterhoeven > cc: Heiko Stuebner > Cc: Lee Jones > Cc: Len Brown > Cc: Pavel Machek > Cc: Philippe R=E9tornaz > Cc: Rafael J. Wysocki > Cc: Romain Perier > Signed-off-by: Guenter Roeck > --- Similarly to the restart handlers, I really like the concept. Acked-by: Heiko Stuebner