PROCESSOR-SDK-AM62X: Question of ti-rpmsg-char scripts, specifically the recv_msg() method

Hi folks,

My question comes from when using the ti-rpmsg-char repo https://git.ti.com/cgit/rpmsg/ti-rpmsg-char/about/ as an application example of rpmsg, and trying to use it in our projects.

In the example it provided (rpmsg-char-simple.c), it performs a ping-pong rpmsg communication between linux core, and remote processor (for example m4f mcu in my case). Basically linux core send to the remote processor, then the remote processor bounce a message back, and repeat this for several times.

I have tried on AM62x board the example works as expected. My observation (please correct if not right) is, the recv_msg() method is a blocking operation, and will hang there if not receiving any message. In the ping-pong communication example this is not of concern since the incoming of message is deterministic (once every sending operation finished / number of messages pre-defined).

In our application, I hope to use the recv_msg() method to handle messages that arrives at random time / of any number, like a listening mode. I modified the scripts and tried to simply call recv_msg() method alone (no longer in a ping-pong manner), while I found if not receving anything, it will hang there and no way to elegantly exit. (ctrl-c will cause the "Application did not close some rpmsg_char devices" message), also not able to operate on other things.

could you provide some advice that if I missed something, or some better practice to use the recv_msg() method?

Regards, 

Wei

My adapted codes are something like below:

#define RPROC_ID_USE 9
// ....
// ....

/**
 * @brief API for linux core get into the mode of receiving incoming rpmsg.
 * 
 * @param dev_name 
 * @param remote_endpt 
 * @return int 
 */
int rpmsg_recv_blob(char* dev_name, int remote_endpt)
{
	int ret = 0;
	int packet_len;
	char eptdev_name[32] = { 0 };
	char packet_buf[128] = { 0 };


	rpmsg_char_dev_t *rcdev;
	int flags = 0;
        /*
         * Open the remote rpmsg device identified by dev_name and bind the
	 * device to a local end-point used for receiving messages from
	 * remote processor
         */
	sprintf(eptdev_name, "rpmsg-char-%d-%d", RPROC_ID_USE, getpid());
	rcdev = rpmsg_char_open(RPROC_ID_USE, dev_name, remote_endpt, eptdev_name, flags);
	if (!rcdev) {
	perror("Can't create an endpoint device");
	return -EPERM;
	}

	ret = recv_msg(rcdev->fd, 128, (char *)packet_buf, &packet_len);
	if (ret < 0) {
		printf("recv_msg failed, ret = %d\n", ret);
		goto out;
	}

	// handle the received data blob
	if (ret >= 0) {
		// ... do something
	}
	goto out;


out:
	ret = rpmsg_char_close(rcdev);
	if (ret < 0)
		perror("Can't delete the endpoint device\n");

	return ret;
}

/********************
and in main():
********************/
int main(int argc, char *argv[])
{
	int ret, status, c;
	int rproc_id = 0;
	int remote_endpt = REMOTE_ENDPT;
	char *dev_name = NULL;

    // .... 
    
	status = rpmsg_recv_blob(dev_name, remote_endpt);

	rpmsg_char_exit();

	return 0;
}