Provided by: linux-doc-2.6.15_2.6.15-23.39_all bug

NAME

       blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage

SYNOPSIS

       int blk_rq_map_user  (request_queue_t * q, struct request * rq,
                              void __user * ubuf, unsigned int len);

ARGUMENTS

       q      request queue where request should be inserted

       rq     request structure to fill

       ubuf   the user buffer

       len    length of user data

DESCRIPTION

       Data will be mapped directly for zero copy io, if possible. Otherwise a
       kernel bounce buffer is used.

       A  matching  blk_rq_unmap_user  must  be issued at the end of io, while
       still in process context.

NOTE

       The mapped bio may need to be bounced through  blk_queue_bounce  before
       being  submitted  to  the  device, as pages mapped may be out of reach.
       It’s the callers responsibility to make sure this happens. The original
       bio must be passed back in to blk_rq_unmap_user for proper unmapping.