[ts-7000] Re: Shared Memory between User Space App and 2.4 Kernel Module

["charliem_1216" <>]

Hi Marv --

--- In  "marv.schwartz" <> wrote:
>
> Hi,
> 
> How can a tslinux 2.4 kernel module and an application both access shared 
> memory? In the app, a shared memory block is created or opened in the the 
> following code:

Take a look at LDD3 here:
http://oreilly.com/catalog/9780596005900/book/index.csp

Especially chapter 15.  Doing this with a char device may be easier (chapter 3).

regards, ........ Charlie

> 
> #define SHMKEY (ftok("KWHdata", 0x1e))
> 
> typedef struct shMem {
>    int state;
>    long elapsedSecs;
>    int counter1;
>    int counter2;
>    int counter3;
>    int counter4;
> } sharedMem;
> 
> sharedMem *getSharedMem() {
>    int shmid = shmget(SHMKEY, sizeof(sharedMem), IPC_CREAT | IPC_EXCL | 
> 0x660); // try to create shared memory
>    if (shmid == -1) shmid = shmget(SHMKEY, sizeof(sharedMem), 0); // create 
> failed--try to use existing shared memory
>    if (shmid == -1) {
>        perror("Error assigning shared memory");
>        exit(1);
>    }
>    return shmat(shmid, 0, 0);
> }
> 
> How is the same shared memory accessed from a tslinux 2.4 kernel module (on a 
> ts-7250)? Are there equivalent routines to ftok and shmget?
> 
> The kernel module increments the counters on interrupts. The app needs 
> read-only access to the counters.
> 
> Thanks,
> 
> Marv
>




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