From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] set a base index for libsas based ata devices Date: Wed, 21 Dec 2016 00:03:42 -0800 Message-ID: <20161221080342.GA21557@infradead.org> References: <1482258634.2475.20.camel@HansenPartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1482258634.2475.20.camel@HansenPartnership.com> Sender: linux-ide-owner@vger.kernel.org To: James Bottomley Cc: Peter Chang , "linux-scsi@vger.kernel.org" , linux-ide@vger.kernel.org List-Id: linux-scsi@vger.kernel.org On Tue, Dec 20, 2016 at 10:30:34AM -0800, James Bottomley wrote: > I'd actually disagree with this assertion; it's why tagging (what you > mean by ncq) and queue depth are separate. Queue depth represents the > number of outstanding commands we sent on the wire; however, it often > excludes things like sense probes and error handling commands, so > tagged depth==1 is a different operating environment from untagged. > Some transports actually have no untagged variant nowadays, so it's > physically impossible to disable tagging. Yes. We have the queue_type sysfs file that also used to be writeable and allow changing the queue type, but it's never been used for anything. For debugging you can clear the tagged_supported flag in the driver, but there should be no reason for doing that during normal operation for a SAS HBA driver.