On Sat, Dec 22, 2001 at 09:06:08AM -0000, Pichai Raghavan wrote: > The board on which I am running linux has 16 MB of which > 0-8 MB is used by Linux and rest of 8-16 MB is used by > another processor running another OS. (basically the > board has 2 CPUs) > > Now I have a driver on Linux that needs to access the 8-16 memory > space to communicate with the other CPU. I am thinking of using these > addresses directly within my driver. My understaning is that since > there is no MMU protection within the kernel my driver can access the > addresses even though they have not been configured for Linux. As far as I know there are also no page table mappings for the unconfigured memory, so you'll have to use ioremap() to create them (see Documentation/IO-mapping.txt). Alternatively, you could use the MTD driver for uncached system RAM and treat the memory for the other OS as a block device (see drivers/mtd/devices/slram.c). Erik -- J.A.K. (Erik) Mouw, Information and Communication Theory Group, Faculty of Information Technology and Systems, Delft University of Technology, PO BOX 5031, 2600 GA Delft, The Netherlands Phone: +31-15-2783635 Fax: +31-15-2781843 Email: J.A.K.Mouw@its.tudelft.nl WWW: http://www-ict.its.tudelft.nl/~erik/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ IRC Channel: irc.openprojects.net / #kernelnewbies Web Page: http://www.kernelnewbies.org/
