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

NAME

       blk_queue_make_request  - define an alternate make_request function for
       a device

SYNOPSIS

       void blk_queue_make_request  (request_queue_t * q,
                                      make_request_fn * mfn);

ARGUMENTS

       q      the request queue for the device to be affected

       mfn    the alternate make_request function

DESCRIPTION

       The  normal way for &struct bios to be passed to a device driver is for
       them to be collected into requests on a  request  queue,  and  then  to
       allow  the  device  driver to select requests off that queue when it is
       ready. This works well for  many  block  devices.  However  some  block
       devices  (typically  virtual  devices such as md or lvm) do not benefit
       from the processing on the request queue, and are served best by having
       the requests passed directly to them. This can be achieved by providing
       a function to blk_queue_make_request.

CAVEAT

       The driver that does this *must* be able  to  deal  appropriately  with
       buffers  in  ‘‘highmemory’’. This can be accomplished by either calling
       __bio_kmap_atomic to get a temporary  kernel  mapping,  or  by  calling
       blk_queue_bounce to create a buffer in normal memory.