Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755580AbYHNPrR (ORCPT ); Thu, 14 Aug 2008 11:47:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751445AbYHNPrG (ORCPT ); Thu, 14 Aug 2008 11:47:06 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:55459 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751373AbYHNPrD (ORCPT ); Thu, 14 Aug 2008 11:47:03 -0400 Date: Thu, 14 Aug 2008 11:47:02 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Oliver Neukum cc: Pavel Machek , , , Linux-pm mailing list , kernel list , Subject: Re: [linux-pm] Power management for SCSI In-Reply-To: <200808141608.13431.oneukum@suse.de> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1452 Lines: 36 On Thu, 14 Aug 2008, Oliver Neukum wrote: > > > 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. What can we do?... Real world devices don't always obey the spec. You could argue that the suspend current should be sufficient to maintain the contents of the cache, which would then be written out after resume. But even if that is true, it's a very fragile guarantee to rely on. > 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. Think of it in two parts: idle-timeout detection and autosuspend. Presumably you don't object to the idle-timeout detection (which is needed for powering down links in general), and you don't argue against the cache-flushing part of autosuspend. Taken together, that's about 90% of my proposal. So what is the objectionable 10%? Alan Stern -- 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/