Make xf86SetDesiredModes aware of current output configuration

By adding a new output callback, ->get_crtc, xf86SetDesiredModes is able to
avoid turning off outputs & CRTCs if the current output<->CRTC mappings are the
same as the desired configuration.  This helps avoid flickering displays at
startup time, which speeds things up a little and looks better.

hw/xfree86/modes/xf86Crtc.c

@@ -2033,6 +2033,72 @@ xf86InitialConfiguration (ScrnInfoPtr scrn, Bool canGrow)
     return TRUE;
 }
 
+/*
+ * Check the CRTC we're going to map each output to vs. it's current
+ * CRTC.  If they don't match, we have to disable the output and the CRTC
+ * since the driver will have to re-route things.
+ */
+static void
+xf86PrepareOutputs (ScrnInfoPtr scrn)
+{
+    xf86CrtcConfigPtr   config = XF86_CRTC_CONFIG_PTR(scrn);
+    int			o;
+
+    for (o = 0; o < config->num_output; o++) {
+	xf86OutputPtr output = config->output[o];
+#if RANDR_GET_CRTC_INTERFACE
+	/* If we can't get the current CRTC, play it safe */
+	if (!output->funcs->get_crtc) {
+	    (*output->funcs->dpms)(output, DPMSModeOff);
+	    continue;
+	}
+	/* Disable outputs that are unused or will be re-routed */
+	if (output->crtc != (*output->funcs->get_crtc)(output) ||
+	    output->crtc == NULL)
+#endif
+	    (*output->funcs->dpms)(output, DPMSModeOff);
+    }
+}
+
+static void
+xf86PrepareCrtcs (ScrnInfoPtr scrn)
+{
+    xf86CrtcConfigPtr   config = XF86_CRTC_CONFIG_PTR(scrn);
+    int			c;
+
+    for (c = 0; c < config->num_crtc; c++) {
+#if RANDR_GET_CRTC_INTERFACE
+	xf86CrtcPtr	crtc = config->crtc[c];
+	xf86OutputPtr	output = NULL;
+	uint32_t	desired_outputs = 0, current_outputs = 0;
+	int		o;
+
+	for (o = 0; o < config->num_output; o++) {
+	    output = config->output[o];
+	    if (output->crtc == crtc)
+		desired_outputs |= (1<<o);
+	    /* If we can't tell where it's mapped, force it off */
+	    if (!output->funcs->get_crtc) {
+		desired_outputs = 0;
+		break;
+	    }
+	    if ((*output->funcs->get_crtc)(output) == crtc)
+		current_outputs |= (1<<o);
+	}
+
+	/*
+	 * If mappings are different or the CRTC is unused,
+	 * we need to disable it
+	 */
+	if (desired_outputs != current_outputs ||
+	    !desired_outputs)
+	    (*crtc->funcs->dpms)(crtc, DPMSModeOff);
+#else
+	(*crtc->funcs->dpms)(crtc, DPMSModeOff);
+#endif
+    }
+}
+
 /*
  * Using the desired mode information in each crtc, set
  * modes (used in EnterVT functions, or at server startup)
@@ -2042,25 +2108,10 @@ _X_EXPORT Bool
 xf86SetDesiredModes (ScrnInfoPtr scrn)
 {
     xf86CrtcConfigPtr   config = XF86_CRTC_CONFIG_PTR(scrn);
-    int			c, o;
+    int			c;
 
-    /*
+    xf86PrepareOutputs(scrn);
-     * Turn off everything so mode setting is done
+    xf86PrepareCrtcs(scrn);
-     * with hardware in a consistent state
-     */
-    for (o = 0; o < config->num_output; o++) 
-    {
-	xf86OutputPtr  output = config->output[o];
-	(*output->funcs->dpms)(output, DPMSModeOff);
-    }
-
-    for (c = 0; c < config->num_crtc; c++) 
-    {
-	xf86CrtcPtr crtc = config->crtc[c];
-
-	crtc->funcs->dpms(crtc, DPMSModeOff);
-	memset(&crtc->mode, 0, sizeof(crtc->mode));
-    }
 
     for (c = 0; c < config->num_crtc; c++)
     {

hw/xfree86/modes/xf86Crtc.h

@@ -424,6 +424,13 @@ typedef struct _xf86OutputFuncs {
     Bool
     (*get_property)(xf86OutputPtr output,
 		    Atom property);
+#endif
+#ifdef RANDR_GET_CRTC_INTERFACE
+    /**
+     * Callback to get current CRTC for a given output
+     */
+    xf86CrtcPtr
+    (*get_crtc)(xf86OutputPtr output);
 #endif
     /**
      * Clean up driver-specific bits of the output

randr/randrstr.h

@@ -55,6 +55,7 @@
 #define RANDR_10_INTERFACE 1
 #define RANDR_12_INTERFACE 1
 #define RANDR_13_INTERFACE 1 /* requires RANDR_12_INTERFACE */
+#define RANDR_GET_CRTC_INTERFACE 1
 
 #define RANDR_INTERFACE_VERSION 0x0103