Date: Mon, 15 Dec 2003 16:32:06 -0800 (PST) From: Dan Strick <strick@covad.net> To: freebsd-scsi@freebsd.org Cc: dan@mist.nodomain Subject: atapicam and residual byte counts Message-ID: <200312160032.hBG0W6TN000505@mist.nodomain>
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While hacking on an ATAPI CD-drive via atapicam, I noticed that the returned data transfer counts for all data input operations (e.g. mode sense) were too high. In fact, they were all equal to the input buffer sizes. A little hacking revealed that the residual byte counts in the CAM CCB for scsi i/o operations were always coming back zero. I did a little test by placing known data in the back end of the input buffer before the input operation and observed that it wasn't being overwritten even though the CAM system claimed the entire buffer was being filled. Then I repeated the tests on a real SCSI drive on a real SCSI host adapter and observed that the residual byte counts in the CAM CCBs were coming back nonzero when this was appropriate. Not knowing the actual transfer length for a data transfer presents a little bit of a challenge. Is atapicam broken? I am running FreeBSD 4.9-Release. Dan Strick strick@covad.net
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