From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: [usb-storage] Re: Make UAS work on HS for devices with and without command tagging support Date: Mon, 19 Dec 2011 11:12:25 -0500 Message-ID: <20111219161225.GO14291@linux.intel.com> References: <1323888472-21035-1-git-send-email-bigeasy@linutronix.de> <20111214225331.GA5508@xanatos> <4EE9B375.4020606@linutronix.de> <20111215211201.GA6482@xanatos> <20111216144724.GC19563@linutronix.de> <20111216201236.GE19563@linutronix.de> <20111216203146.GN14291@linux.intel.com> <20111216204241.GA30915@linutronix.de> <20111216213628.GA5509@xanatos> <1324072059.10429.27.camel@dabdike> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1324072059.10429.27.camel@dabdike> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: James Bottomley Cc: Sarah Sharp , Sebastian Andrzej Siewior , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, USB Storage List List-Id: linux-scsi@vger.kernel.org On Fri, Dec 16, 2011 at 10:47:39PM +0100, James Bottomley wrote: > Well, no, what you want to do is use a shared tag map at the block > level. That will manage a joint tag space for N queues without your > having to partition it arbitrarily. see scsi_host_find_tag() and > scsi_init_shared_tag_map(). By the way, the same verbiage about tags being shared across LUNs is also present in the SAS spec (and various other specs last time I looked, which wasn't recently). We should probably make this the default in the SCSI core. I suspect it hasn't bitten us because there are so few multi-LUN devices out there, and it's only a "May" check, not "Must" check. But Linux is technically in violation of the SAS spec by sending two commands to the same target with the same tag. -- 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