On Mon, 4 Feb 2008 18:39:22 -0800 (PST) Luben Tuikov <ltuikov@xxxxxxxxx> wrote: > --- On Mon, 2/4/08, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > > There are 3 usages of sense handling in drivers > > > > 1. sense is available in driver internal structure and is > > mem-copied to upper level > > 2. A CHECK_CONDITION status was returned and the driver > > uses the scsi_eh_prep_cmnd() > > for a REQUEST_SENSE invocation to the target. Then > > returning the sense in > > scsi_eh_return_cmnd(). A variation on this is when the > > driver does nothing the queue > > is frozen an the scsi watchdog timer does the above. > > 3. The underline host adapter does the REQUEST_SENSE and a > > pre-allocated and DMA mapped > > sense buffer receives the sense information from HW. > > Many years ago when "ACA" had a constructive meaning, > so did "Autosense". Then about 5 years ago, "Autosense" > disappeared completely since it became the de facto > implementation of the then SCSI Execute Command "RPC", > now just SCSI Execute Command procedure call. > > At that point in time, the SCSI mid-layer decided > to embrace this model and give the LLDD a scsi command > structure which included the sense data buffer to > a size that the SCSI mid-layer was interested in, > at the moment 96 bytes, macro defined in > include/scsi/scsi_cmnd.h. > > The concept of "Autosense" was off-loaded to LLDD > to emulate it if the specific target device to > which the command was issued, didn't supply the > sense data on CHECK CONDITION, and more so > relevant to target devices which implemented > queuing, thus the ACA. > > And the mid-layer would consider extracting > the sense data via REQUEST SENSE command > as a _special case_ if the LLDD/transport layer > didn't implement the "autosense" model. Only SPI and USB? The most of LLDs using the transport protocol that we care about today uses sense buffer in their own internal structure. I think that the issue to solve to kill scsi_cmnd:sense_buffer is how to share (or export) such sense buffer with the scsi mid-layer. For the old transport protocols, we could do something that James said in this thread to to kill scsi_cmnd:sense_buffer. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
