Problem with map_user_kiobuf() not mapping to physical memory

[Terry Barnaby <terry@beam.demon.co.uk>]

We are developing a Linux driver which allows a device to read/write
directly
into a processes virtual memory space.
I have a question on using map_user_kiobuf() as we are having problems.
I was under the impression that if I used map_user_kiobuf() this would
map
the users virtual address space into locked physical memory pages so
that
I/O could be performed.
However, I note that if the user just mallocs memory and does not access
it
(No physical memory pages created) and then passes this virtual address
space
to the driver which performs a map_user_kiobuf() on it, the resulting
kiobuf
structure has all of the pagelist[] physical address entries set to the
same value
and the maplist[] entries set to 0. The devices access to this memory
now
causes system problems.
Is map_user_kiobuf() working correctly ?
Should I call some function to map the virtual address space into
physical memory
or at least pages before I call map_user_kiobuf() ?

Cheers

Terry

--
  Dr Terry Barnaby                     BEAM Ltd
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