On 05/08/2018 08:44 AM, Bodo Stroesser wrote: > Hi, > > We are going to use TCMUser for an emulation of tape devices and > media chargers. > > Generally target core and TCMUser seem to work fine for this purpose. > But there is at least one situation, where TCMUser as well as the target core > currently are not able to support sequential access device emulation > correctly. > > The situation is when an initiator sends a SCSI READ CDB with a length that is > greater than the length of the tape block to read. We can distinguish two > subcases: > > A) The initiator sent the READ CDB without the SILI bit being set. > In this case the sequential access device has to transfer the data from the > tape block (only the length of the tape block) and transmit a good status. > The current interface between TCMUser and the userspace does not support > reduction of the read data size by the userspace program. > > The patch/RFC below fixes this subcase by allowing the userspace program to > specify a reduced data size in read direction. > > B) The initiator sent the READ CDB with the SILI bit not being set. > In this case the sequential access device has to transfer the data from the > tape block as in A), but additionally has to transmit CHECK CONDITION with > the ILI bit set and NO SENSE in the sensebytes. The information field in > the sensebytes must contain the residual count. > With the below patch/RFC a user space program can specify the real read > data length and appropriate sensebytes. > But AFAICS, up to now the target core is not prepared to transfer datas > _and_ sensebytes for a single SCSI command. Therefore only the status > and sensebytes are transferred, but no data. > > I fear, fixing this would result in more invasive patches. Suggestions > how to fix would be welcome. > > > This patch was created for kernel 4.15.9. > > Best regards, > Bodo > > --- > ... Have you tried this with my target core patch? Just curious if short reads would work with my patch and this code. -- Lee Duncan -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
