drm/edid: add block count and data helper functions for drm_edid

Add drm_edid based block count and data access helper functions that
take the EDID allocated size into account.

At the moment, the allocated size should always match the EDID size
indicated by the extension count, but this will change in the future.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1a68c8667a88e7c451b001ad8bd86c8badb57fb8.1654674560.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -1613,6 +1613,35 @@ static const void *edid_extension_block_data(const struct edid *edid, int index)
 	return edid_block_data(edid, index + 1);
 }
 
+static int drm_edid_block_count(const struct drm_edid *drm_edid)
+{
+	int num_blocks;
+
+	/* Starting point */
+	num_blocks = edid_block_count(drm_edid->edid);
+
+	/* Limit by allocated size */
+	num_blocks = min(num_blocks, (int)drm_edid->size / EDID_LENGTH);
+
+	return num_blocks;
+}
+
+static int drm_edid_extension_block_count(const struct drm_edid *drm_edid)
+{
+	return drm_edid_block_count(drm_edid) - 1;
+}
+
+static const void *drm_edid_block_data(const struct drm_edid *drm_edid, int index)
+{
+	return edid_block_data(drm_edid->edid, index);
+}
+
+static const void *drm_edid_extension_block_data(const struct drm_edid *drm_edid,
+						 int index)
+{
+	return edid_extension_block_data(drm_edid->edid, index);
+}
+
 /*
  * Initializer helper for legacy interfaces, where we have no choice but to
  * trust edid size. Not for general purpose use.
@@ -1665,8 +1694,8 @@ static const void *__drm_edid_iter_next(struct drm_edid_iter *iter)
 	if (!iter->drm_edid)
 		return NULL;
 
-	if (iter->index < edid_block_count(iter->drm_edid->edid))
-		block = edid_block_data(iter->drm_edid->edid, iter->index++);
+	if (iter->index < drm_edid_block_count(iter->drm_edid))
+		block = drm_edid_block_data(iter->drm_edid, iter->index++);
 
 	return block;
 }
@@ -3574,22 +3603,21 @@ static int add_detailed_modes(struct drm_connector *connector,
 const u8 *drm_find_edid_extension(const struct drm_edid *drm_edid,
 				  int ext_id, int *ext_index)
 {
-	const struct edid *edid = drm_edid ? drm_edid->edid : NULL;
 	const u8 *edid_ext = NULL;
 	int i;
 
 	/* No EDID or EDID extensions */
-	if (!edid || !edid_extension_block_count(edid))
+	if (!drm_edid || !drm_edid_extension_block_count(drm_edid))
 		return NULL;
 
 	/* Find CEA extension */
-	for (i = *ext_index; i < edid_extension_block_count(edid); i++) {
-		edid_ext = edid_extension_block_data(edid, i);
+	for (i = *ext_index; i < drm_edid_extension_block_count(drm_edid); i++) {
+		edid_ext = drm_edid_extension_block_data(drm_edid, i);
 		if (edid_block_tag(edid_ext) == ext_id)
 			break;
 	}
 
-	if (i >= edid_extension_block_count(edid))
+	if (i >= drm_edid_extension_block_count(drm_edid))
 		return NULL;
 
 	*ext_index = i + 1;