drm/i915: clarify preferred sdvo input mode code

- kill intel_sdvo->input_dtd, it's only used as a temporary variable,
  we store the preferred input mode in the adjusted mode at mode_fixup
  time.
- rename the function to make it clear what we want it to do (get the
  preferred mode) and say in a comment what it unfortunately does as a
  side-effect (set the new output timings).
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_sdvo.c

@@ -140,9 +140,6 @@ struct intel_sdvo {
 
 	/* DDC bus used by this SDVO encoder */
 	uint8_t ddc_bus;
-
-	/* Input timings for adjusted_mode */
-	struct intel_sdvo_dtd input_dtd;
 };
 
 struct intel_sdvo_connector {
@@ -949,11 +946,15 @@ intel_sdvo_set_output_timings_from_mode(struct intel_sdvo *intel_sdvo,
 	return true;
 }
 
+/* Asks the sdvo controller for the preferred input mode given the output mode.
+ * Unfortunately we have to set up the full output mode to do that. */
 static bool
-intel_sdvo_set_input_timings_for_mode(struct intel_sdvo *intel_sdvo,
+intel_sdvo_get_preferred_input_mode(struct intel_sdvo *intel_sdvo,
 				    struct drm_display_mode *mode,
 				    struct drm_display_mode *adjusted_mode)
 {
+	struct intel_sdvo_dtd input_dtd;
+
 	/* Reset the input timing to the screen. Assume always input 0. */
 	if (!intel_sdvo_set_target_input(intel_sdvo))
 		return false;
@@ -965,10 +966,10 @@ intel_sdvo_set_input_timings_for_mode(struct intel_sdvo *intel_sdvo,
 		return false;
 
 	if (!intel_sdvo_get_preferred_input_timing(intel_sdvo,
-						   &intel_sdvo->input_dtd))
+						   &input_dtd))
 		return false;
 
-	intel_sdvo_get_mode_from_dtd(adjusted_mode, &intel_sdvo->input_dtd);
+	intel_sdvo_get_mode_from_dtd(adjusted_mode, &input_dtd);
 
 	return true;
 }
@@ -989,7 +990,7 @@ static bool intel_sdvo_mode_fixup(struct drm_encoder *encoder,
 		if (!intel_sdvo_set_output_timings_from_mode(intel_sdvo, mode))
 			return false;
 
-		(void) intel_sdvo_set_input_timings_for_mode(intel_sdvo,
+		(void) intel_sdvo_get_preferred_input_mode(intel_sdvo,
 							   mode,
 							   adjusted_mode);
 	} else if (intel_sdvo->is_lvds) {
@@ -997,7 +998,7 @@ static bool intel_sdvo_mode_fixup(struct drm_encoder *encoder,
 							     intel_sdvo->sdvo_lvds_fixed_mode))
 			return false;
 
-		(void) intel_sdvo_set_input_timings_for_mode(intel_sdvo,
+		(void) intel_sdvo_get_preferred_input_mode(intel_sdvo,
 							   mode,
 							   adjusted_mode);
 	}