Try the vremap() call in your RTL module:
shmem = (SHMEM_ST *) vremap(SHMEM_BASE_ADDRESS,sizeof(SHMEM_ST));
don't forget to call vfree() in your module clean-up:
vfree(shmem);
In the 2.2-version you'll need the __va() macro to serve the same purpose.
-Don
On Tue, 8 Jun 1999, Estabridis, Janet P wrote:
> Hi,
> I have read all the old messages on shared memory and nothing has helped.
>
> I have been attempting to use shared memory as is spelled out in the paper
> "Using Shared Memory in Real-Time Linux" by Fredrick M. Proctor and in your
> "HOWTO." I am confused and if you have any suggestions I'd appreciate it.
>
> 1. I have gotten shared memory to work with two non-real time applications.
> But, when I try and add a rt application the real-time application appears
> to be accessing different memory because if I write a new value to the
> shared memory the applications don't see it. I have verified that the
> pointer to memory in the real-time application and the pointers in the linux
> applications all contain the same address. I did this by passing the rt_ptr
> through a FIFO to the non-real time application and doing an fprintf.
>
> what I mean is that the user_ptr = (BLOCK *) mmap ( .... ) from the linux
> applications is the same as the address pointer in the real-time application
> char *rt_ptr = ADDRESS
>
> So, why aren't the accessing the same memory?? user_ptr = 0x7d00000 and
> rt_ptr = 0x7d00000 but why doesn't the application see it when the rt
> process initializes the block structure to a value ?? i.e. rt_ptr->block[0]=
> 500 or rt_ptr->block[10] = 444;
>
> I use a common header file where
>
> struct {
> unsigned short block[5000];
> } BLOCK;
>
> Any suggestions ??
>
> I am using Kernel 2.0.36 and RTL v1.1
> I have 128Mbytes of memory on a pentinum II and I want to use close to
> 4Bytes maximum eventually, so my lilo.conf has append="mem=125m"
>
> I am very new to Linux so would appreciate any help in finding the answer.
>
> Thanks
>
>
> Janet Estabridis
> Electrical Engineer
> NAWC Code 473E00D
> China Lake, CA 93555
> (760) 939-2896 FAX (760) 939 -3075
>
>
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