How to attach to physical memory

[Michael A. Petonic]

In article <193 at focsys.UUCP> larry at focsys.UUCP (Larry Williamson) writes:
 >How does one get access to a memory buffer that is hard wired to a
 >physical memory location outside of the normal system memory?
 > [...]
 >If I use this technique, I must tell my driver to use a physical memory
 >buffer, but I do not understand how to tell my driver to read from
 >physical address 0xa00000. 
 >
 >I am using Bell Tech's Unix system V/386.
 >
 >Thanks,
 >   Larry

Since Bell Tech's UNIX system V/386 is close to our's (INTERACTIVE's
386/ix (see various articles describing the ancestry)), I looked in
our ``Writing 386/ix Device Drivers'' book and it mentions the
macros ``phystokv()'' and ``kvtophys()'' which map between physical
addresses and kernel virtual addresses.  They are defined in
<sys/immu.h>.  This should be relevant to Bell Tech's system.

-MikeP
--------
Michael A. Petonic                      (213) 453-8649 x3247
INTERACTIVE Systems Corporation         "My opinions in no way influence
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