Date: Thu, 11 Nov 2010 15:28:45 +0200 From: Alexander Motin <mav@FreeBSD.org> To: Joerg Schilling <Joerg.Schilling@fokus.fraunhofer.de> Cc: freebsd-scsi@FreeBSD.org, freebsd-current@FreeBSD.org, freebsd-stable@FreeBSD.org, marius@alchemy.franken.de Subject: Re: Sense fetching [Was: cdrtools /devel ...] Message-ID: <4CDBEF8D.5080001@FreeBSD.org> In-Reply-To: <4cdbece1.EWYSqdvnx6XWF8EF%Joerg.Schilling@fokus.fraunhofer.de> References: <4CD45209.5010607@FreeBSD.org> <20101105192028.GA68728@alchemy.franken.de> <4cd822df.o/wBtwsNCXiy8xZn%Joerg.Schilling@fokus.fraunhofer.de> <4CD82E2A.3070407@FreeBSD.org> <4cd8320a.U7/OjtLLBVtE4dTy%Joerg.Schilling@fokus.fraunhofer.de> <4CD83535.1010008@FreeBSD.org> <4cdbbfef.v4cr/k2jZr9gdpyF%Joerg.Schilling@fokus.fraunhofer.de> <4CDBC55B.1040307@FreeBSD.org> <4cdbc65f.bo%2BmYNFB2GPwXmq7%Joerg.Schilling@fokus.fraunhofer.de> <4CDBEA8B.1020306@FreeBSD.org> <4cdbece1.EWYSqdvnx6XWF8EF%Joerg.Schilling@fokus.fraunhofer.de>
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Joerg Schilling wrote: > Alexander Motin <mav@FreeBSD.org> wrote: > >>> Compare the number of sense bytes I like to request (18) with the number >>> previous FreeBSD versions did actually request. It is obvious that in case >>> there is a resid reported onm an old kernel, libscg (with your chanhge) would >>> believe that probably less that the absolute minumum of sense data is available. >> Kernel code I have changed affects only controllers without automatic >> sense fetching. For such controllers CAM previously always reported zero >> sense_resid, independently of requested size (which actually was also >> ignored in this case). So previously whatever you asked for 18 or 32 >> bytes - sense_resid was always zero, like if you got full 18 or 32 >> bytes. That was wrong. Now, in the same situation, if device wants to >> return let's say 20 bytes -- you will get 0 and 12 bytes of sense_resid >> respectively, meaning 18 and 20 bytes of received sense. >> >> AFAIK sense_resid always measured from the requested sense_len. In my >> patch for libscg you may see that I have changed both request and >> response paths. Resulted sense_count should be absolutely the same. > > What is the requested size with the various HBAs in earlier kernels? For HBAs with automatic sense fetching -- as passed in sence_len request field. In case of libscg it was SSD_FULL_SIZE before and I've set it to be real value now. Returned sense_resid should be real in both cases, respecting submitted sense_len. For HBAs without sense fetching, CAM was always requesting SSD_FULL_SIZE and returned fake zero sense_resid, like if it just completely fulfilled sense_len from request. Now it should start honor sense_len on request and return real sense_resid on reply, relative to sense_len. -- Alexander Motin
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