pipe.c

#include <sys/types.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <native/pipe.h>

#define PIPE_MINOR 0

/* User-space side */

int pipe_fd;

int main(int argc, char *argv[])
{
        char devname[32], buf[16];

        /* ... */

        sprintf(devname, "/dev/rtp%d", PIPE_MINOR);
        pipe_fd = open(devname, O_RDWR);

        if (pipe_fd < 0)
                fail();

        /* Wait for the prompt string "Hello"... */
        read(pipe_fd, buf, sizeof(buf));

        /* Then send the reply string "World": */
        write(pipe_fd, "World", sizeof("World"));

        /* ... */
}

void cleanup(void)
{
        close(pipe_fd);
}

/* Kernel-side */

#define TASK_PRIO  0            /* Highest RT priority */
#define TASK_MODE  T_FPU|T_CPU(0)       /* Uses FPU, bound to CPU #0 */
#define TASK_STKSZ 4096         /* Stack size (in bytes) */

RT_TASK task_desc;

RT_PIPE pipe_desc;

void task_body(void)
{
        RT_PIPE_MSG *msgout, *msgin;
        int err, len, n;

        for (;;) {
                /* ... */

                len = sizeof("Hello");
                /* Get a message block of the right size in order to
                   initiate the message-oriented dialog with the
                   user-space process. Sending a continuous stream of
                   bytes is also possible using rt_pipe_stream(), in
                   which case no message buffer needs to be
                   preallocated. */
                msgout = rt_pipe_alloc(len);

                if (!msgout)
                        fail();

                /* Send prompt message "Hello" (the output buffer will be freed
                   automatically)... */
                strcpy(RT_PIPE_MSGPTR(msgout), "Hello");
                rt_pipe_send(&pipe_desc, msgout, len, P_NORMAL);

                /* Then wait for the reply string "World": */
                n = rt_pipe_receive(&pipe_desc, &msgin, TM_INFINITE);

                if (n < 0) {
                        printf("receive error> errno=%d\n", n);
                        continue;
                }
        
                if (n == 0) {
                        if (msg == NULL) {
                                printf("pipe closed by peer while reading\n");
                                continue;
                        }

                        printf("empty message received\n");
                } else
                        printf("received msg> %s, size=%d\n", P_MSGPTR(msg),
                               P_MSGSIZE(msg));

                /* Free the received message buffer. */
                rt_pipe_free(&pipe_desc, msgin);

                /* ... */
        }
}

init init_module(void)
{
        int err;

        err = rt_pipe_create(&pipe_desc, NULL, PIPE_MINOR);

        if (err)
                fail();

        /* ... */

        err = rt_task_create(&task_desc,
                             "MyTaskName", TASK_STKSZ, TASK_PRIO, TASK_MODE);
        if (!err)
                rt_task_start(&task_desc, &task_body, NULL);

        /* ... */
}

void cleanup_module(void)
{
        rt_pipe_delete(&pipe_desc);
        rt_task_delete(&task_desc);
}

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