Alexander Motin <mav_at_FreeBSD.org> wrote: > >>> Given the fact that many drives will probably only return 18 bytes of sense > >>> data, this will happen every time libscg is told to fetch more sense than the > >>> drive is willing to return. > >>> > >>> Is there a way to distinct an old kernel from a new one? > >> I don't see the problem. Previous kernel in most cases reported > >> sesnse_resid == 0, lying that there is more sense data then really is. > >> New one should report real (often positive) value. In both cases > >> sesnse_resid value measured from the value submitted to the kernel. > > > > Did the old kernel return a zero sense_resid for any implemented SCSI > > transport? Libscg is a generic SCSI transport library and cdrecord is just one > > user of this lib. > > Not sure I understand your question. Zero sesnse_resid is absolutely > normal situation if device gave same amount of sense as application > requested. As I can see, many of SCSI controllers report sesnse_resid > properly. I may assume that some, like atapicd don't -- in that case > you'll also see 0 there. FreeBSD-CAM did try to fetcth more than 18 bytes of sense data and it may be that some drives did return only 18 bytes. In this case, I would asume that there is a resid > 0. > > Do you know the CAM behavior for other SCSI transports? > > I don't have real SCSI CD to test, but a as I can see, most of SCSI > controllers return sense data automatically. Sense fetching changes > should not affect/break anything there. The question still remains whether the previous implementation did return resid > 0 in some cases. In this case, I would need to implement both variants in the libscg adaption layer and I would need to know whether I am running on an old version or on a new version kernel. Do you know of a simple method to implement this distinction? Jörg -- EMail:joerg_at_schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin js_at_cs.tu-berlin.de (uni) joerg.schilling_at_fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/ URL: http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schilyReceived on Thu Nov 11 2010 - 09:05:40 UTC
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