media: cec-notifier: small improvements

Allow calling cec_notifier_set_phys_addr and
cec_notifier_set_phys_addr_from_edid with a NULL notifier, in which
case these functions do nothing.

Add a cec_notifier_phys_addr_invalidate helper function (the notifier
equivalent of cec_phys_addr_invalidate).

These changes simplify drm CEC driver support.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/include/media/cec-notifier.h b/include/media/cec-notifier.h
index 298f996..a4f7429 100644
--- a/include/media/cec-notifier.h
+++ b/include/media/cec-notifier.h
@@ -57,6 +57,7 @@
  * @pa: the CEC physical address
  *
  * Set a new CEC physical address.
+ * Does nothing if @n == NULL.
  */
 void cec_notifier_set_phys_addr(struct cec_notifier *n, u16 pa);
 
@@ -66,6 +67,7 @@
  * @edid: the struct edid pointer
  *
  * Parses the EDID to obtain the new CEC physical address and set it.
+ * Does nothing if @n == NULL.
  */
 void cec_notifier_set_phys_addr_from_edid(struct cec_notifier *n,
 					  const struct edid *edid);
@@ -118,4 +120,17 @@
 
 #endif
 
+/**
+ * cec_notifier_phys_addr_invalidate() - set the physical address to INVALID
+ *
+ * @n: the CEC notifier
+ *
+ * This is a simple helper function to invalidate the physical
+ * address. Does nothing if @n == NULL.
+ */
+static inline void cec_notifier_phys_addr_invalidate(struct cec_notifier *n)
+{
+	cec_notifier_set_phys_addr(n, CEC_PHYS_ADDR_INVALID);
+}
+
 #endif