rtc: nvmem: return error values

In case of error, make rtc_nvmem_register() able to return an error value
to its caller.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/nvmem.c

@@ -84,21 +84,23 @@ static void rtc_nvram_unregister(struct rtc_device *rtc)
 /*
  * New ABI, uses nvmem
  */
-void rtc_nvmem_register(struct rtc_device *rtc,
+int rtc_nvmem_register(struct rtc_device *rtc,
 		       struct nvmem_config *nvmem_config)
 {
 	if (!nvmem_config)
-		return;
+		return -ENODEV;
 
 	nvmem_config->dev = &rtc->dev;
 	nvmem_config->owner = rtc->owner;
 	rtc->nvmem = nvmem_register(nvmem_config);
 	if (IS_ERR_OR_NULL(rtc->nvmem))
-		return;
+		return PTR_ERR(rtc->nvmem);
 
 	/* Register the old ABI */
 	if (rtc->nvram_old_abi)
 		rtc_nvram_register(rtc, nvmem_config->size);
+
+	return 0;
 }
 
 void rtc_nvmem_unregister(struct rtc_device *rtc)

drivers/rtc/rtc-core.h

@@ -48,11 +48,14 @@ static inline const struct attribute_group **rtc_get_dev_attribute_groups(void)
 #endif
 
 #ifdef CONFIG_RTC_NVMEM
-void rtc_nvmem_register(struct rtc_device *rtc,
+int rtc_nvmem_register(struct rtc_device *rtc,
 		       struct nvmem_config *nvmem_config);
 void rtc_nvmem_unregister(struct rtc_device *rtc);
 #else
-static inline void rtc_nvmem_register(struct rtc_device *rtc,
-				      struct nvmem_config *nvmem_config) {}
+static inline int rtc_nvmem_register(struct rtc_device *rtc,
+				     struct nvmem_config *nvmem_config)
+{
+	return -ENODEV;
+}
 static inline void rtc_nvmem_unregister(struct rtc_device *rtc) {}
 #endif