On 11/05/2013 05:19 PM, nidhi mittal hada wrote: > My doubt is :- > When we know block device driver , request structure, request queue > operation .. as per LDD. > How and where the request structure we are getting in scsi layer > fits/relates to thi sblock layer request structure.... > > is the sequence ..block device layer request function -> calls scsi > layer request function ? > > The links below show how block layer request connect to scsi request, but In Chinese, sorry, but you may find clue in the code section. http://blog.csdn.net/fudan_abc/article/details/1966510 http://blog.csdn.net/fudan_abc/article/details/1966538 http://blog.csdn.net/fudan_abc/article/details/1967045 http://blog.csdn.net/fudan_abc/article/details/1967050 BTW: Why not use dm-crypt? Jack > > > > > > On Tue, Nov 5, 2013 at 6:34 PM, nidhi mittal hada > <nidhimittal19@xxxxxxxxx <mailto:nidhimittal19@xxxxxxxxx>> wrote: > > _*Setting of sd_prep_fn()*_ > sd_probe is called*/whenever a/* */new scsi device is attached to > the system. /* > > sd_probe calls -> sd_probe_async-> > inside sd_probe_async, request prep fn is set to *sd_prep_fn* > >>>>like this blk_queue_prep_rq(sdp->request_queue, sd_prep_fn); > > > _*Calling of sd_prep_fn*_ > ????? > > Is this request queue sdp->request_queue, different from the request > queue, > for which scsi_prep_fn is used?? > > Are they on different layers ? > > Is there some relation between them ? > > > > Thanks > Nidhi > > > On Tue, Nov 5, 2013 at 6:13 PM, nidhi mittal hada > <nidhimittal19@xxxxxxxxx <mailto:nidhimittal19@xxxxxxxxx>> wrote: > > scsi_alloc_sdev(must be called once for each scsi device) -->calls > scsi_alloc_queue (that sets up sdev->request_queue > sets up scsi_request_fn and > sets up req prep function as > scsi_prep_fn) > > 1738 struct request_queue *scsi_alloc_queue(struct scsi_device > *sdev) > 1739 { > 1740 struct request_queue *q; > 1742 q = __scsi_alloc_queue(sdev->host, > scsi_request_fn);>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> > 1743 if (!q) > 1744 return NULL; > 1746 blk_queue_prep_rq(q, > scsi_prep_fn);>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> > 1747 blk_queue_softirq_done(q, scsi_softirq_done); > 1748 blk_queue_rq_timed_out(q, scsi_times_out); > 1749 blk_queue_lld_busy(q, scsi_lld_busy); > 1750 return q; > 1751 } > And after this call sdev_request_queue is allocated................ > > Now, scsi_request_fn should be called while processing each > request in this sdev->request_queue... > Please correct me if i m wrong. > Now, inside scsi_request_fn, we get next queueable request by > calling > blk_peek_request - to fetch request from request queue .. > > blk_peek_request -> calls __elv_next_request to fetch next request- > and calls prep_rq_fn(q, rq); > > > *which is scsi_prep_fn not the sd_prep_fn isnt it ??* > > > Then where is sd_prep_fn is used for ?? > > Thanks > Nidhi > > > > > On Tue, Nov 5, 2013 at 5:39 PM, Jack Wang <xjtuwjp@xxxxxxxxx > <mailto:xjtuwjp@xxxxxxxxx>> wrote: > > Hi Nidhi, > > About the function call trace you can use ftrace to find > out, another > useful tool is scsi_logging_level to set more verbose > logging output for > scsi core. > > Regards > Jack > On 11/05/2013 12:48 PM, nidhi mittal hada wrote: > > > > Hi All > > > > i have got a requirement where I need to encrypt/decrypt > data that goes > > from scsi layer to a particular block device. > > As per my understanding till now on scsi subsystem in > linux, i think i > > need to > > use crypto api and call appropriate encrypt/decrypt > function from sd > > driver for block device. > > > > I need to locate that specific function where this change > needs to be > > made ... > > I know basic block device driver writing in linux .. But > not able to fit > > scsi in this picture. > > > > I have few basic doubts.. kindly help in resolving ... > > > > 1) Now, as example block device driver sbull, as given > LDD, works on > > request queue, fetches req from this queue, using function > req = > > elv_next_request(q)), > > in request function. > > what is corresponding function in sd layer ? > > That is the function where i have req->buffer in hand with > me.. > > > > > > 2) For a write operation from initiator to disk > > is the hierarchy like this > > *sd_prep_fn* > > generic block device request structure -> converted into > scsi specific > > request structure > > OR > > what is scsi_prep_fn for?? > > > > 3)How is Scpnt pointer that is req-> special is used in > sd_prep_func.. > > is processed? i mean which layer picks Scpnt up and > processes ?? > > > > 4)Any document any URL any kind of instruction will be > extremely helpful. > > > > 5)Whenever a *new scsi device is attached *sd_probe is called > > sd_async_probe() is the async part of sd_probe() So when > this is called > > the prep_fn is set to sd_prep_fn and hence this will be > called. > > > > *But i thought sd_prep_fn should be called for each and > every request > > .....??* > > Kindly help me to clear the confusion .. > > > > > > Thanks > > Nidhi > > > > > > > > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies@xxxxxxxxxxxxxxxxx > <mailto:Kernelnewbies@xxxxxxxxxxxxxxxxx> > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > > > > > > > > -- > Thanks & Regards > Nidhi Mittal Hada > > http://nidhi-searchingmyself.blogspot.com/ > > > > > -- > Thanks & Regards > Nidhi Mittal Hada > > http://nidhi-searchingmyself.blogspot.com/ > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
