Wiktor Grebla wrote in the comedi mailing list:

Wiktor Grebla wrote in the comedi mailing list:
Somwhere around 2.6.9 kernel remap_pfn_range() was introduced as a
portable replacement for remap_page_range,
presumably with some wrapper which has dissapeared recently (2.6.11),
what resulted in "Unknown symbol" while
loading comedi module (and the following ones because of the symbols in it).
I've changed include/linux/mm.h slightly, hopefully without breaking
anything.
Seems to work. I've tested it with 2.6.10 and 2.6.11.