From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 5 Jul 2012 21:05:26 -0600 From: Matthew Wilcox To: Alan Stern Cc: James Bottomley , Linus Torvalds , Hans de Goede , Ben Hutchings , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , "akpm@linux-foundation.org" , "alan@lxorguk.ukuu.org.uk" , Matthew Dharm , Greg Kroah-Hartman , linux-scsi Subject: Re: [ 38/48] SCSI & usb-storage: add try_rc_10_first flag Message-ID: <20120706030525.GC17681@parisc-linux.org> References: <20120703203512.GE28804@parisc-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thu, Jul 05, 2012 at 05:40:45PM -0400, Alan Stern wrote: > On Tue, 3 Jul 2012, Matthew Wilcox wrote: > > > I think the necessary algorithm is simpler than that: > > > > Send RC10 (unless the device supports PI, in which case it's probably > > enterprisey and well-tested) > > Send RC16 > > If RC10 capacity agrees with RC16 capacity, use extra RC16 data. > > (for values of "agrees with" that include the "-1 to use RC16" indicator) > > > > Sure, it's one extra command, but really, who cares? > > Well, some USB devices might care. Right now we don't send RC16 to > them at all because they get RC10 first and it indicates a capacity > below 2 TB. Mmm. I think I forgot a step: Send RC10 (unless the device supports PI, in which case it's probably enterprisey and well-tested) If the device indicates a level < SPC_2, stop here Send RC16 If RC10 capacity agrees with RC16 capacity, use extra RC16 data. (for values of "agrees with" that include the "-1 to use RC16" indicator) > In the end, usb-storage may be forced to use the NO_READ_CAPACITY_16 > flag with all devices except those we can positively identify as a > USB-(S)ATA bridge. Is that really an improvement over nobbling the IDENTIFY results to force SCSI_2? -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."