@@ -777,38 +777,44 @@ static void intel_find_lvds_downclock(struct drm_device *dev,
* If it is present, return 1.
* If it is not present, return false.
* If no child dev is parsed from VBT, it assumes that the LVDS is present.
- * Note: The addin_offset should also be checked for LVDS panel.
- * Only when it is non-zero, it is assumed that it is present.
*/
-static int lvds_is_present_in_vbt(struct drm_device *dev)
+static bool lvds_is_present_in_vbt(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
- struct child_device_config *p_child;
- int i, ret;
+ int i;
if (!dev_priv->child_dev_num)
- return 1;
+ return true;
- ret = 0;
for (i = 0; i < dev_priv->child_dev_num; i++) {
- p_child = dev_priv->child_dev + i;
- /*
- * If the device type is not LFP, continue.
- * If the device type is 0x22, it is also regarded as LFP.
+ struct child_device_config *child = dev_priv->child_dev + i;
+
+ /* If the device type is not LFP, continue.
+ * We have to check both the new identifiers as well as the
+ * old for compatibility with some BIOSes.
*/
- if (p_child->device_type != DEVICE_TYPE_INT_LFP &&
- p_child->device_type != DEVICE_TYPE_LFP)
+ if (child->device_type != DEVICE_TYPE_INT_LFP &&
+ child->device_type != DEVICE_TYPE_LFP)
continue;
- /* The addin_offset should be checked. Only when it is
- * non-zero, it is regarded as present.
+ /* However, we cannot trust the BIOS writers to populate
+ * the VBT correctly. Since LVDS requires additional
+ * information from AIM blocks, a non-zero addin offset is
+ * a good indicator that the LVDS is actually present.
*/
- if (p_child->addin_offset) {
- ret = 1;
- break;
- }
+ if (child->addin_offset)
+ return true;
+
+ /* But even then some BIOS writers perform some black magic
+ * and instantiate the device without reference to any
+ * additional data. Trust that if the VBT was written into
+ * the OpRegion then they have validated the LVDS's existence.
+ */
+ if (dev_priv->opregion.vbt)
+ return true;
}
- return ret;
+
+ return false;
}
/**