From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Hancock Subject: Re: Do we need to implement sr START/STOP management Date: Tue, 01 Nov 2011 19:13:16 -0600 Message-ID: <4EB0992C.5070309@gmail.com> References: <1320126812.7701.17.camel@dabdike> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-gx0-f174.google.com ([209.85.161.174]:65011 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753542Ab1KBBNT (ORCPT ); Tue, 1 Nov 2011 21:13:19 -0400 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: JiSheng Zhang Cc: James Bottomley , linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org On 11/01/2011 12:35 AM, JiSheng Zhang wrote: > Hi James, > > 2011/11/1 James Bottomley: >> On Tue, 2011-11-01 at 13:31 +0800, JiSheng Zhang wrote: >>> Currently, there's no start/stop management in scsi cdrom driver to >>> spin up/down the motor do we need to implement it? >> >> Say more ... like what you think it buys. The auto spin down of a CD >> tends to be the best power control we have and it's not even clear that >> manufacturers have implemented any other useful power states. > > Does it mean the behavior depends on manufacturers? Some cd will spin > down automatically? Even so, how about during shutdown just after reading > something from cdrom? > > Thanks, > Jisheng I believe the main reason disks are stopped during shutdown is that for many hard drives that use head unloading, it's much better for the lifespan of the drive to do a powered head unload on software command before powering off than an emergency unload caused by a loss of power. I don't believe that optical drives have such an issue.