drm/i915: Don't set up HDMI ports that aren't in the BIOS device table.

Use the child device array to decide whether the given HDMI output should be
initialized. If the given HDMI port can't be found in child device array,
it is not present and won't be initialized.
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_hdmi.c

@@ -225,7 +225,52 @@ static const struct drm_encoder_funcs intel_hdmi_enc_funcs = {
 	.destroy = intel_hdmi_enc_destroy,
 };
 
-
+/*
+ * Enumerate the child dev array parsed from VBT to check whether
+ * the given HDMI is present.
+ * 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 given
+ * HDMI is present.
+ */
+int hdmi_is_present_in_vbt(struct drm_device *dev, int hdmi_reg)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct child_device_config *p_child;
+	int i, hdmi_port, ret;
+
+	if (!dev_priv->child_dev_num)
+		return 1;
+
+	if (hdmi_reg == SDVOB)
+		hdmi_port = DVO_B;
+	else if (hdmi_reg == SDVOC)
+		hdmi_port = DVO_C;
+	else if (hdmi_reg == HDMIB)
+		hdmi_port = DVO_B;
+	else if (hdmi_reg == HDMIC)
+		hdmi_port = DVO_C;
+	else if (hdmi_reg == HDMID)
+		hdmi_port = DVO_D;
+	else
+		return 0;
+
+	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 HDMI, continue.
+		 */
+		if (p_child->device_type != DEVICE_TYPE_HDMI)
+			continue;
+		/* Find the HDMI port */
+		if (p_child->dvo_port == hdmi_port) {
+			ret = 1;
+			break;
+		}
+	}
+	return ret;
+}
 void intel_hdmi_init(struct drm_device *dev, int sdvox_reg)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -233,6 +278,10 @@ void intel_hdmi_init(struct drm_device *dev, int sdvox_reg)
 	struct intel_output *intel_output;
 	struct intel_hdmi_priv *hdmi_priv;
 
+	if (!hdmi_is_present_in_vbt(dev, sdvox_reg)) {
+		DRM_DEBUG_KMS("HDMI is not present. Ignored it \n");
+		return;
+	}
 	intel_output = kcalloc(sizeof(struct intel_output) +
 			       sizeof(struct intel_hdmi_priv), 1, GFP_KERNEL);
 	if (!intel_output)