Add proper protocol version checks.

cmd.c

 
 	/* Check if everything is within limits */
 	switch (v->cmd) {
-	case CMD_PROTOCOL_PREAMBLE:
-		if (!streq(data->device.protocol_ver, "2.4")) {
-			if (!quiet) {
-				fprintf(stderr, "WARNING: Device protocol is %s but this program is tested with 2.4 only.\n",
-					data->device.protocol_ver);
-				fprintf(stderr, "         Please report successes/failures to author's email: georgi@unixsol.org\n");
-				fprintf(stderr, "         You may use -q or --quiet to suppress the message.\n");
-			}
-		}
-		break;
 	case CMD_VIDEOHUB_DEVICE:
 		if (!data->device.dev_present) {
 			die("Device reports that it's not present.");

videohubctrl.c

 }
 
 static void print_device_desc(struct device_desc *d) {
-	if (!strlen(d->protocol_ver) || !strlen(d->model_name))
-		die("The device does not return protocol version and model name!");
 	printf("\n");
 	printf("Protocol version: %s\n", d->protocol_ver);
 	printf("Model name: %s\n", d->model_name);
 		exit(EXIT_FAILURE);
 
 	read_device_command_stream(data);
+
+	if (!strlen(data->device.protocol_ver) || !strlen(data->device.model_name))
+		die("The device does not respond correctly. Is it Videohub?");
+
+	if (strstr(data->device.protocol_ver, "2.") != data->device.protocol_ver)
+		die("Device protocol is %s but this program supports 2.x only.\n",
+			data->device.protocol_ver);
+
 	if (show_monitor) {
 		while (1) {
 			printf("\e[2J\e[H"); // Clear screen