Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760006AbYHNOH2 (ORCPT ); Thu, 14 Aug 2008 10:07:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752464AbYHNOHN (ORCPT ); Thu, 14 Aug 2008 10:07:13 -0400 Received: from ns2.suse.de ([195.135.220.15]:58848 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752042AbYHNOHL convert rfc822-to-8bit (ORCPT ); Thu, 14 Aug 2008 10:07:11 -0400 From: Oliver Neukum Organization: Novell To: Pavel Machek Subject: Re: [linux-pm] Power management for SCSI Date: Thu, 14 Aug 2008 16:08:12 +0200 User-Agent: KMail/1.9.9 Cc: linux-pm@lists.linux-foundation.org, Alan Stern , James.Bottomley@hansenpartnership.com, "Linux-pm mailing list" , kernel list , teheo@novell.com References: <200808131821.30564.oneukum@suse.de> <20080814135021.GE2262@elf.ucw.cz> In-Reply-To: <20080814135021.GE2262@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT Content-Disposition: inline Message-Id: <200808141608.13431.oneukum@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1599 Lines: 37 Am Donnerstag 14 August 2008 15:50:21 schrieb Pavel Machek: > On Wed 2008-08-13 18:21:29, Oliver Neukum wrote: > > Am Mittwoch 13 August 2008 17:44:46 schrieb Alan Stern: > > > > All children that are USB must be powered down. We know in fact that most > > > > drives don't care that the device is suspended. The problem was drive > > > > enclosures that cut power upon suspension losing cached data. > > > > > > You misunderstood my question. ?Are there SCSI transports other than > > > USB sharing the requirement that all child devices must be suspended > > > before the link can be powered down? > > > > I dispute that USB in general has this property. Some storage devices > > need their caches flushed. USB itself is perfectly happy with autosuspending > > the storage device (host) without telling the disks (devices) > > > > You could even argue that these storage devices violate the USB spec. > > Hmm... but suspended devices have very little power budget, right? > > So unless you have external power supply (2.5" frames generally > don't), you can't really suspend and stay spinned up... > True, but the spec says that no state shall be lost. I don't really argue against flushing the caches. But I cannot that this would demand that we should implement autopsuspend for SCSI. It seems like overengineering to me. Regards Oliver -- 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/