From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [Patch] SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails Date: Tue, 11 Oct 2011 12:41:34 +0200 Message-ID: <4E941D5E.6060101@suse.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Amit Sahrawat Cc: James Bottomley , Alan Stern , Douglas Gilbert , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christoph Hellwig , NamJae Jeon List-Id: linux-scsi@vger.kernel.org On 10/11/2011 10:26 AM, Amit Sahrawat wrote: > SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails > > It has been observed that a number of USB HDD's do not respond correc= tly > to SCSI mode sense command(retrieve caching pages) which results in t= heir > Write Cache being discarded by queue requests i.e., WCE if left set t= o > '0'(disabled). So, in order to identify the devices correctly - give = it > a last try using SG_ATA_16 after failure from normal routine. > I'd be _VERY_ cautious when trying something like this. ATA_16 is a rather recent command, and most older drives simply=20 can't cope with this. Instead they just kick the error handler and=20 go offline eventually. Shouldn't we rather use a sensible default, ie assume WCE is enabled? Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare-l3A5Bk7waGM@public.gmane.org +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html