Subject: [Patch] drm/i915: try another two possible DDC bus for the SDVO device with multiple outputs
---
 drivers/gpu/drm/i915/intel_sdvo.c |   42 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

Index: linux-2.6/drivers/gpu/drm/i915/intel_sdvo.c
===================================================================
--- linux-2.6.orig/drivers/gpu/drm/i915/intel_sdvo.c	2009-12-15 23:32:23.000000000 +0800
+++ linux-2.6/drivers/gpu/drm/i915/intel_sdvo.c	2009-12-15 23:58:50.000000000 +0800
@@ -124,6 +124,8 @@
 
 	/* DDC bus used by this SDVO output */
 	uint8_t ddc_bus;
+	/* the possible DDC bus for multi outputs */
+	uint8_t possible_bus[2];
 
 	/* Mac mini hack -- use the same DDC as the analog connector */
 	struct i2c_adapter *analog_ddc_bus;
@@ -1627,6 +1629,36 @@
 	edid = drm_get_edid(&intel_output->base,
 			    intel_output->ddc_bus);
 
+	if (edid == NULL && intel_sdvo_multifunc_encoder(intel_output)) {
+		uint8_t saved_ddc = sdvo_priv->ddc_bus;
+		/* try the first DDC1 */
+		if (sdvo_priv->possible_bus[0]) {
+			sdvo_priv->ddc_bus = sdvo_priv->possible_bus[0];
+			edid = drm_get_edid(&intel_output->base,
+			    		intel_output->ddc_bus);
+		}
+		if (edid != NULL) {
+			/*
+			 * update the DDC bus for external monitor if EDID
+			 * can be obtained.
+			 * If it is not right, please fix me.
+			 */
+			sdvo_priv->ddc_bus = sdvo_priv->possible_bus[0];
+		}
+		/*
+		 * If there is no EDID and exists the DDC2 bus, we will try to
+		 * use it to read the edid
+		 */
+		if (edid == NULL && sdvo_priv->possible_bus[1]) {
+			sdvo_priv->ddc_bus = sdvo_priv->possible_bus[1];
+			edid = drm_get_edid(&intel_output->base,
+			    		intel_output->ddc_bus);
+		}
+		if (edid == NULL) {
+			/* If there is no EDID, restore the saved ddc */
+			sdvo_priv->ddc_bus = saved_ddc;
+		}
+	}
 	/* when there is no edid and no monitor is connected with VGA
 	 * port, try to use the CRT ddc to read the EDID for DVI-connector
 	 */
@@ -2159,6 +2191,16 @@
 
 	/* Corresponds to SDVO_CONTROL_BUS_DDCx */
 	dev_priv->ddc_bus = 1 << num_bits;
+	if (num_bits == 3) {
+		dev_priv->possible_bus[0] = 2;
+		dev_priv->possible_bus[1] = 4;
+	} else if (num_bits == 2) {
+		dev_priv->possible_bus[0] = 2;
+		dev_priv->possible_bus[1] = 0;
+	} else {
+		dev_priv->possible_bus[0] = 0;
+		dev_priv->possible_bus[1] = 0;
+	}
 }
 
 static bool