Provided by:
kernel-doc-2.4.27_2.4.27-12_all 
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 buffer_heads 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", either by calling bh_kmap to get a kernel
mapping, to by calling create_bounce to create a buffer in normal
memory.