centos man page for blk_queue_prep_rq

BLK_QUEUE_PREP_RQ(9)						   Block Devices					      BLK_QUEUE_PREP_RQ(9)

NAME
       blk_queue_prep_rq - set a prepare_request function for queue

SYNOPSIS
       void blk_queue_prep_rq(struct request_queue * q, prep_rq_fn * pfn);

ARGUMENTS
       q
	   queue

       pfn
	   prepare_request function

DESCRIPTION
       It's possible for a queue to register a prepare_request callback which is invoked before the request is handed to the request_fn. The goal
       of the function is to prepare a request for I/O, it can be used to build a cdb from the request data for instance.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						      BLK_QUEUE_PREP_RQ(9)