drm/edid: add iterator for EDID base and extension blocks

Add an iterator abstraction for going through all the EDID blocks.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ce02778b353b906c928268de9d7569d493a9be5d.1651569697.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -1599,6 +1599,54 @@ static const void *edid_extension_block_data(const struct edid *edid, int index)
 	return edid_block_data(edid, index + 1);
 }
 
+/*
+ * EDID base and extension block iterator.
+ *
+ * struct drm_edid_iter iter;
+ * const u8 *block;
+ *
+ * drm_edid_iter_begin(edid, &iter);
+ * drm_edid_iter_for_each(block, &iter) {
+ *         // do stuff with block
+ * }
+ * drm_edid_iter_end(&iter);
+ */
+struct drm_edid_iter {
+	const struct edid *edid;
+
+	/* Current block index. */
+	int index;
+};
+
+static void drm_edid_iter_begin(const struct edid *edid,
+				struct drm_edid_iter *iter)
+{
+	memset(iter, 0, sizeof(*iter));
+
+	iter->edid = edid;
+}
+
+static const void *__drm_edid_iter_next(struct drm_edid_iter *iter)
+{
+	const void *block = NULL;
+
+	if (!iter->edid)
+		return NULL;
+
+	if (iter->index < edid_block_count(iter->edid))
+		block = edid_block_data(iter->edid, iter->index++);
+
+	return block;
+}
+
+#define drm_edid_iter_for_each(__block, __iter)			\
+	while (((__block) = __drm_edid_iter_next(__iter)))
+
+static void drm_edid_iter_end(struct drm_edid_iter *iter)
+{
+	memset(iter, 0, sizeof(*iter));
+}
+
 static const u8 edid_header[] = {
 	0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00
 };