Support failing modeset

chromeos/display/output_configurator.cc

Index: chromeos/display/output_configurator.cc
diff --git a/chromeos/display/output_configurator.cc b/chromeos/display/output_configurator.cc
index 67da273b64965469c0b9d252e2e64e3c8ab16158..a143c409f0a1834458417407d40658f27d794527 100644
--- a/chromeos/display/output_configurator.cc
+++ b/chromeos/display/output_configurator.cc
@@ -941,28 +941,74 @@ bool OutputConfigurator::EnterState(
 
   // Finally, apply the desired changes.
   DCHECK_EQ(cached_outputs_.size(), updated_outputs.size());
+  bool all_succeeded = true;
   if (!updated_outputs.empty()) {
     delegate_->CreateFrameBuffer(width, height, updated_outputs);
     for (size_t i = 0; i < updated_outputs.size(); ++i) {
       const OutputSnapshot& output = updated_outputs[i];
-      if (delegate_->ConfigureCrtc(output.crtc, output.current_mode,
-                                   output.output, output.x, output.y)) {
-        if (output.touch_device_id)
-          delegate_->ConfigureCTM(output.touch_device_id, output.transform);
-        cached_outputs_[i] = updated_outputs[i];
-      } else {
+      bool configure_succeeded;
+
+      while (true) {
+        configure_succeeded = false;

[Daniel Erat, 2014/01/09 00:40:34]

nit: just initialize the variable to false where it's defined outside of the
loop; that way you can set it to true when you break out of the loop on success
but not need to set it to false in the multiple places where you break out of
the loop on failure

+        if (delegate_->ConfigureCrtc(output.crtc, output.current_mode,
+                                       output.output, output.x, output.y)) {
+          configure_succeeded = true;
+          break;
+        }
+
         LOG(WARNING) << "Unable to configure CRTC " << output.crtc << ":"
                      << " mode=" << output.current_mode
                      << " output=" << output.output
                      << " x=" << output.x
                      << " y=" << output.y;
+
+        const ModeInfo* mode_info = GetModeInfo(output, output.current_mode);
+        if (!mode_info)
+          break;
+
+        // Find the mode with the next-best resolution and see if that can
+        // be set.
+        int best_mode_pixels = 0;
+
+        int current_mode_pixels = mode_info->width * mode_info->height;
+        for (ModeInfoMap::const_iterator it = output.mode_infos.begin();
+             it != output.mode_infos.end(); it++) {
+          int pixel_count = it->second.width * it->second.height;
+          if ((pixel_count < current_mode_pixels) &&
+              (pixel_count > best_mode_pixels)) {
+            updated_outputs[i].current_mode = it->first;
+            best_mode_pixels = pixel_count;
+          }
+        }
+
+        if (best_mode_pixels == 0)
+          break;
       }
+
+      if (configure_succeeded) {
+        if (output.touch_device_id)
+          delegate_->ConfigureCTM(output.touch_device_id, output.transform);
+        cached_outputs_[i] = updated_outputs[i];
+      } else {
+        all_succeeded = false;
+      }
+
+      // If we are trying to set mirror mode and one of the modesets fails,
+      // then the two monitors will be mis-matched.  In this case, return
+      // false to let the observers be aware.
+      if (output_state == STATE_DUAL_MIRROR &&
+          output_power[i] &&
+          output.current_mode != output.mirror_mode)
+        all_succeeded = false;
+
     }
   }
 
-  output_state_ = output_state;
-  power_state_ = power_state;
-  return true;
+  if (all_succeeded)  {
+    output_state_ = output_state;
+    power_state_ = power_state;
+  }
+  return all_succeeded;
 }
 
 OutputState OutputConfigurator::ChooseOutputState(