I'm trying to mmap /dev/mem in python to access various registers on a
gumstix overo (with an omap 3530 processor). Here is the code I'm
using (as a minimal example):
----------------------------
import os, mmap
MAP_MASK = mmap.PAGESIZE - 1
addr = (see below)
f = os.open("/dev/mem", os.O_RDWR | os.O_SYNC)
m = mmap.mmap(f, mmap.PAGESIZE, mmap.MAP_SHARED, mmap.PROT_WRITE |
mmap.PROT_READ, offset=addr & ~MAP_MASK)
m.seek(addr & MAP_MASK)
c = m.read_byte()
print c
m.close()
os.close(f)
----------------------------
If I use: addr = 0x48002178 everything works swimmingly. However, if I
use: addr = 0x48088024 (or all the addresses I've tried > 0x48044000)
I get the following error
Unhandled fault: external abort on non-linefetch (0x1018) at 0x40020024
Bus error
and python crashes. I'm basing the mmap flags and options off of
devmem2.c. If I remove the O_SYNC flag from the os.open command, I can
read and write to registers fine, but randomly I will get the
Unhandled fault error and things will not work correctly.
Am I using the right command to write to the omap registers? should I
be using the O_SYNC flag? Any ideas where these errors are coming
from?
Thanks in advance for your help.
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