Add an IOCTL method to the RTC interface

arch/arm/src/stm32/stm32_rtc_lowerhalf.c

@@ -118,6 +118,7 @@ static const struct rtc_ops_s g_rtc_ops =
   .rdwkalm    = NULL,
   .setwkalm   = NULL,
 #endif
+  .ioctl      = NULL,
   .destroy    = NULL,
 };
 

drivers/timers/rtc.c

@@ -502,8 +502,18 @@ static int rtc_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
       break;
 #endif /* CONFIG_RTC_ALARM */
 
+    /* Forward any unrecognized IOCTLs to the lower half driver... they
+     * may represent some architecture-specific command.
+     */
+
     default:
-      ret = -ENOTTY;
+      {
+        ret = -ENOTTY;
+        if (ops->ioctl)
+          {
+            ret = ops->ioctl(upper->lower, cmd, arg);
+          }
+      }
       break;
     }
 

include/nuttx/rtc.h

@@ -261,6 +261,16 @@
 
 #define RTC_WKALM_SET      _RTCIOC(0x0010)
 
+/* Architecture-specific RTC IOCTLS should begin at RTC_USER_IOCBASE.  For
+ * example:
+ *
+ *   #define MY_RTC_IOCTL1 _RTCIOC(RTC_USER_IOCBASE);
+ *   #define MY_RTC_IOCTL2 _RTCIOC(RTC_USER_IOCBASE + 1);
+ *   etc.
+ */
+
+#define RTC_USER_IOCBASE   0x0011
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
@@ -406,6 +416,11 @@ struct rtc_ops_s
                        FAR const struct rtc_wkalrm *wkalrm);
 #endif
 
+   /* Support for architecture-specific RTC operations */
+
+  CODE int (*ioctl)(FAR struct rtc_lowerhalf_s *lower, int cmd,
+                    unsigned long arg);
+   
    /* The driver has been unlinked and there are no further open references
     * to the driver.
     */