From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zhang Rui Subject: Re: [RFC PATCH 4/6] PM / Runtime: Introduce flag can_power_off Date: Tue, 14 Feb 2012 15:11:29 +0800 Message-ID: <1329203489.19384.39.camel@rui.sh.intel.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mga14.intel.com ([143.182.124.37]:57074 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753131Ab2BNHLm (ORCPT ); Tue, 14 Feb 2012 02:11:42 -0500 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Alan Stern Cc: "Rafael J. Wysocki" , Lin Ming , Jeff Garzik , Tejun Heo , Len Brown , linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org Hi, Alan, On =E4=B8=80, 2012-02-13 at 15:41 -0500, Alan Stern wrote: > On Mon, 13 Feb 2012, Rafael J. Wysocki wrote: >=20 > > > I'm not sure if this is really the right approach. What you're t= rying=20 > > > to do is implement two different low-power states, basically D3ho= t and=20 > > > D3cold. Currently the runtime PM core doesn't support such thing= s; all=20 > > > it knows about is low power and full power. > >=20 > > I'd rather say all it knows about is "suspended" and "active", whic= h mean > > "the device is not processing I/O" and "the device may be processin= g I/O", > > respectively. A "suspended" device may or may not be in a low-powe= r state, > > but the runtime PM core doesn't care about that. >=20 > Yes, okay. We can say that this patch tries to implement two differe= nt=20 > "suspended" states, basically "low power" and "power off" (or D3hot a= nd=20 > D3cold). >=20 Right! > > > Before doing an ad-hoc implementation, it would be best to step b= ack > > > and think about other subsystems. Other sorts of devices may wel= l have > > > multiple low-power states. What's the best way for this to be > > > supported by the PM core? > >=20 > > Well, I honestly don't think there's any way they all can be covere= d at the > > same time and that's why we chose to support only "suspended" and "= active" > > as defined above. The handling of multiple low-power states must b= e > > implemented outside of the runtime PM core (like in the PCI core, f= or example). >=20 > That's the point. If this is to be implemented outside of the runtim= e > PM core, should the patch be allowed to add new fields to struct > dev_pm_info (which has to be shared among all subsystems)? >=20 Surely it shouldn't in this case. > Or to put it another way, if we do add new fields to struct dev_pm_in= fo > (like can_power_off) in order to help support multiple "suspended" =20 > states, shouldn't these new fields be such that they can be used by > many different subsystems rather than being special for the > full-power/no-power situation? >=20 My opinion is that the concept of "no-power state" is unique for all devices/buses/platforms. If any of them support this, they can use the routines without any confusion. thanks, rui -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html