kernel: fix error propagation for device deferred initialization

This fix propagates the failure code returned from the device
initialization function to the application. Previously, do_device_init()
mistakely returned errno instead of -errno. We use an intermediate variable
to compute the value to store in dev->state->init_res, and return the
value from the device's init untouched.

Signed-off-by: Loic Domaigne <tech@domaigne.com>

Author: ljd42

kernel/init.c

@@ -313,20 +313,16 @@ static int do_device_init(const struct device *dev)
 
 	if (dev->ops.init != NULL) {
 		rc = dev->ops.init(dev);
-		/* Mark device initialized. If initialization
-		 * failed, record the error condition.
-		 */
+		/* If initialization failed, record the error condition. */
 		if (rc != 0) {
-			if (rc < 0) {
-				rc = -rc;
-			}
-			if (rc > UINT8_MAX) {
-				rc = UINT8_MAX;
-			}
-			dev->state->init_res = rc;
+			__ASSERT(rc != INT_MIN, "init(dev) failed, but init_res will be 0");
+			int res = (rc < 0) ? -rc : rc;
+
+			dev->state->init_res = (res <= UINT8_MAX) ? res : UINT8_MAX;
 		}
 	}
 
+	/* device initialization has been invoked */
 	dev->state->initialized = true;
 
 	if (rc == 0) {