Help with writting from a memory mapped device to disc on linux

[alex_zak_il]

Hello.
I want to write from the memory of a memory-mapped device directly to hard disc directly, without going through RAM (to increase efficiency). Also I need to do the reverse, to write from disc to the memory mapped device.
How can I do it?

I heard that it is impossible on Linux, because there is a risk that someone will swap out to virtual memory the memory-mapped device. Is this true? Is there a way around it?
-thanks, Alex.

[gwalters]

If its a memory mapped device isnt it in the RAM in the first place??

[alex_zak_il]

Yes, I think it is in the RAM. But I heard that it can not be accessed like RAM is accessed out of fear that it will get swapped out.