diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 990acc20771a..40e2cc4e7419 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -1038,6 +1038,10 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 		DRM_DEBUG_KMS("No general definition block is found, no devices defined.\n");
 		return;
 	}
+	/* Remember to keep this in sync with child_device_config;
+	 * whenever a new feature is added to BDB that causes that
+	 * struct to grow this needs to be updated too
+	 */
 	if (bdb->version < 195) {
 		expected_size = 33;
 	} else if (bdb->version == 195) {
@@ -1051,7 +1055,8 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 	}
 
 	if (expected_size > sizeof(*p_child)) {
-		DRM_ERROR("child_device_config cannot fit in p_child\n");
+		DRM_ERROR("child_device_config (size %u) cannot fit in p_child (size %u); bdb->version: %u\n",
+			  expected_size, sizeof(*p_child), bdb->version);
 		return;
 	}
 
diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index f7ad6a585129..71cb96f77870 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -239,6 +239,10 @@ struct common_child_dev_config {
 	u8 not_common2[2];
 	u8 ddc_pin;
 	u16 edid_ptr;
+	u8 obsolete;
+	u8 flags_1;
+	u8 not_common3[13];
+	u8 iboost_level;
 } __packed;
 
 /* This field changes depending on the BDB version, so the most reliable way to