Hi All ,, I will add some more info as i debug further. If i give offset in range 0- 1023 then it work for me. ##################################################### # ./arm.out 1023 w 3 /dev/mem opened. Memory mapped at address 0x40022000. Value at address 0x3FF (0x400223ff): 0xE1 Written 0x3; readback 0xE1 ^C ################################################### # ./arm.out 1024 w 3 /dev/mem opened. Memory mapped at address 0x40022000. Value at address 0x400 (0x40022400): 0x3000000 Written 0x3; readback 0x3 ^C ################################################# Also If i open mmap as private then i can write at 0 offset. ################################################## # ./arm_priv 0 w 9 /dev/mem opened. Memory mapped at address 0x40022000. Value at address 0x0 (0x40022000): 0xEA000006 Written 0x9; readback 0x9 ##################################################### thanks. On Wed, Sep 22, 2010 at 8:06 AM, vinit dhatrak <vinit.dhatrak@xxxxxxxxx> wrote: > > > On Tue, Sep 21, 2010 at 10:21 PM, Mulyadi Santosa > <mulyadi.santosa@xxxxxxxxx> wrote: >> >> Hi.... >> >> On Wed, Sep 22, 2010 at 01:01, vinit dhatrak <vinit.dhatrak@xxxxxxxxx> >> wrote: >> > I guess this issue has something to do with '/dev/mem' being physical >> > memory. The address may have different value when data is set and >> > different >> > data when value is read due to page swapping or copy-on-write. I am just >> > taking wild guess here, please correct me if I am wrong. >> >> I was thinking, it could be that /dev/mem is made as "read only" in >> the architecture...or ...you're hitting memory region which is >> protected. >> > > then the program would have seg-faulted, no? > >> >> -- >> regards, >> >> Mulyadi Santosa >> Freelance Linux trainer and consultant >> >> blog: the-hydra.blogspot.com >> training: mulyaditraining.blogspot.com > > -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
