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From: jody@shell.com (Jody Winston)
Newsgroups: comp.sys.m68k
Subject: using shared memory to talk to physical memory on a Motorala 147
Message-ID: <JODY.89Dec5121254@robulus.shell.com>
Date: 5 Dec 89 18:12:54 GMT
Sender: usenet@shell.com
Distribution: comp.sys.m68k
Organization: Shell Development Company, Bellaire Research Center, Houston, TX
Lines: 45

I'm having trouble talking to physical shared memory on a Motorola 147
V/68 system.  I get the id with:

   if ((id = shmget(key, 
		    0x0c, 
		    (IPC_CREAT | IPC_PHYS | IPC_NOCLEAR | IPC_CI),
		    (int)(0xff00 | 0xffff00) )) == -1)
   {
      perror ("shmget");
      exit (-1);
   }
   
And then set the permissions:

   buf.shm_perm.mode = 0666;
   
   if (shmctl(id, IPC_SET, &buf) == -1)
   {
      perror ("shmctl");
      exit (-1);
   }
   
And then map for read and write:

   if ((addr = shmat(id,
		     (char *)0,
		     (0) )) == (char *)-1)
   {
      perror ("shmctl");
      exit (-1);
   }
   
The address is different, than 0xff00, but I expected this due to
virtual to phsyical translation.  When I try to read or write to this
address I get a bus error:

   printf("Address = 0X%X\t Data = 0X%X\n", addr, *addr);



--
Jody Winston		jody@shell.uucp
...!{sun,psuvax1,bcm,rice,decwrl,cs.utexas.edu}!shell!jody
Shell Development Company, Bellaire Research Center
P.O. Box 481, Room 2202, Houston, TX 77001	(Voice: 713 663-2993)