examples: linux: check rpmsg dev bind status

Check rpmsg device driver override and if correct driver
is already bound, then execute rest of application. If driver
is not bound, then bind rpmsg char driver.

Signed-off-by: Tanmay Shah <[email protected]>

examples/linux/common/common.c

@@ -66,20 +66,48 @@ char *get_rpmsg_ept_dev_name(const char *rpmsg_char_name,
 int bind_rpmsg_chrdev(const char *rpmsg_dev_name)
 {
 	char fpath[256];
-	char *rpmsg_chdrv = "rpmsg_chrdev";
+	const char *rpmsg_chdrv = "rpmsg_chrdev";
+	char drv_override[64] = {0};
 	int fd;
 	int ret;
 
 	/* rpmsg dev overrides path */
 	sprintf(fpath, "%s/devices/%s/driver_override",
 		RPMSG_BUS_SYS, rpmsg_dev_name);
 	printf("open %s\n", fpath);
-	fd = open(fpath, O_WRONLY);
+	fd = open(fpath, O_RDWR);
 	if (fd < 0) {
 		fprintf(stderr, "Failed to open %s, %s\n",
 			fpath, strerror(errno));
 		return -EINVAL;
 	}
+
+	ret = read(fd, drv_override, sizeof(drv_override));
+	if (ret < 0) {
+		fprintf(stderr, "Failed to read %s (%s)\n",
+			fpath, strerror(errno));
+		close(fd);
+		return ret;
+	}
+
+	printf("current drv override = %s\n", drv_override);
+
+	/*
+	 * Check driver override. If "rpmsg_chrdev" string is
+	 * found, then don't attempt to bind. If null string is found,
+	 * then no driver is bound, and attempt to bind rpmsg char driver.
+	 * Any other case, fail binding driver, as device is busy.
+	 */
+	if (strncmp(drv_override, rpmsg_chdrv, strlen(rpmsg_chdrv)) == 0) {
+		close(fd);
+		return 0;
+	} else if (strncmp(drv_override, "(null)", strlen("(null)")) != 0) {
+		printf("error: device %s is busy, drv bind=%s\n",
+		       rpmsg_dev_name, drv_override);
+		close(fd);
+		return -EBUSY;
+	}
+
 	ret = write(fd, rpmsg_chdrv, strlen(rpmsg_chdrv) + 1);
 	if (ret < 0) {
 		fprintf(stderr, "Failed to write %s to %s, %s\n",

examples/linux/rpmsg-echo-test/echo_test.c

@@ -120,6 +120,7 @@ int main(int argc, char *argv[])
 		fprintf(stderr, "access(%s): %s\n", fpath, strerror(errno));
 		return -EINVAL;
 	}
+
 	ret = bind_rpmsg_chrdev(rpmsg_dev);
 	if (ret < 0)
 		return ret;

examples/linux/rpmsg-mat-mul/mat_mul_demo.c

@@ -156,6 +156,7 @@ int main(int argc, char *argv[])
 		fprintf(stderr, "access(%s): %s\n", fpath, strerror(errno));
 		return -EINVAL;
 	}
+
 	ret = bind_rpmsg_chrdev(rpmsg_dev);
 	if (ret < 0)
 		return ret;