Allow for missing or disabled compat_output

When the compat output is missing (I don't think this is actually
possible), or is disabled (and hence has no crtc), we would like to
avoid dereferencing NULL pointers. This patch creates inline functions
to extract the current compat output, crtc or associated RandR crtc
structure, carefully checking for NULL pointers everywhere.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>
(cherry picked from commit de86a3a3448f0a55c1cd99aee9ea80070a589877)

4 files changed, 46 insertions, 17 deletions

diff --git a/hw/xfree86/common/xf86cmap.c b/hw/xfree86/common/xf86cmap.c
index edd5ae9b0..f60d96e7d 100644
--- a/hw/xfree86/common/xf86cmap.c
+++ b/hw/xfree86/common/xf86cmap.c
@@ -1001,8 +1001,7 @@ xf86ChangeGammaRamp(
     CMapLinkPtr pLink;
 
     if (xf86_crtc_supports_gamma(pScrn)) {
-	xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(pScrn);
-	RRCrtcPtr crtc = config->output[config->compat_output]->crtc->randr_crtc;
+	RRCrtcPtr crtc = xf86CompatRRCrtc(pScrn);
 
 	if (crtc) {
 	    if (crtc->gammaSize != size)
@@ -1076,8 +1075,7 @@ xf86GetGammaRampSize(ScreenPtr pScreen)
     CMapScreenPtr pScreenPriv;
 
     if (xf86_crtc_supports_gamma(pScrn)) {
-	xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(pScrn);
-	RRCrtcPtr crtc = config->output[config->compat_output]->crtc->randr_crtc;
+	RRCrtcPtr crtc = xf86CompatRRCrtc(pScrn);
 
 	if (crtc)
 	    return crtc->gammaSize;
@@ -1106,8 +1104,7 @@ xf86GetGammaRamp(
     int shift, sigbits;
 
     if (xf86_crtc_supports_gamma(pScrn)) {
-	xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(pScrn);
-	RRCrtcPtr crtc = config->output[config->compat_output]->crtc->randr_crtc;
+	RRCrtcPtr crtc = xf86CompatRRCrtc(pScrn);
 
 	if (crtc) {
 	    if (crtc->gammaSize < size)
diff --git a/hw/xfree86/modes/xf86Crtc.c b/hw/xfree86/modes/xf86Crtc.c
index 937064003..334fad424 100644
--- a/hw/xfree86/modes/xf86Crtc.c
+++ b/hw/xfree86/modes/xf86Crtc.c
@@ -2571,8 +2571,8 @@ xf86SetDesiredModes (ScrnInfoPtr scrn)
 	if (!crtc->enabled)
 	    continue;
 
-	if (config->output[config->compat_output]->crtc == crtc)
-	    output = config->output[config->compat_output];
+	if (xf86CompatOutput(scrn) && xf86CompatCrtc(scrn) == crtc)
+	    output = xf86CompatOutput(scrn);
 	else
 	{
 	    for (o = 0; o < config->num_output; o++)
@@ -2692,14 +2692,16 @@ xf86SetSingleMode (ScrnInfoPtr pScrn, DisplayModePtr desired, Rotation rotation)
 {
     xf86CrtcConfigPtr	config = XF86_CRTC_CONFIG_PTR(pScrn);
     Bool		ok = TRUE;
-    xf86OutputPtr	compat_output = config->output[config->compat_output];
-    DisplayModePtr	compat_mode;
+    xf86OutputPtr	compat_output;
+    DisplayModePtr	compat_mode = NULL;
     int			c;
 
     /*
      * Let the compat output drive the final mode selection
      */
-    compat_mode = xf86OutputFindClosestMode (compat_output, desired);
+    compat_output = xf86CompatOutput(pScrn);
+    if (compat_output)
+	compat_mode = xf86OutputFindClosestMode (compat_output, desired);
     if (compat_mode)
 	desired = compat_mode;
     
@@ -2894,7 +2896,7 @@ xf86OutputSetEDID (xf86OutputPtr output, xf86MonPtr edid_mon)
     }
 
     /* Set the DDC properties for the 'compat' output */
-    if (output == config->output[config->compat_output])
+    if (output == xf86CompatOutput(scrn))
         xf86SetDDCproperties(scrn, edid_mon);
 
 #ifdef RANDR_12_INTERFACE
diff --git a/hw/xfree86/modes/xf86Crtc.h b/hw/xfree86/modes/xf86Crtc.h
index 9baa956a3..68a968cc2 100644
--- a/hw/xfree86/modes/xf86Crtc.h
+++ b/hw/xfree86/modes/xf86Crtc.h
@@ -689,6 +689,32 @@ extern _X_EXPORT int xf86CrtcConfigPrivateIndex;
 
 #define XF86_CRTC_CONFIG_PTR(p)	((xf86CrtcConfigPtr) ((p)->privates[xf86CrtcConfigPrivateIndex].ptr))
 
+static _X_INLINE xf86OutputPtr
+xf86CompatOutput(ScrnInfoPtr pScrn)
+{
+    xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(pScrn);
+    return config->output[config->compat_output];
+}
+
+static _X_INLINE xf86CrtcPtr
+xf86CompatCrtc(ScrnInfoPtr pScrn)
+{
+    xf86OutputPtr compat_output = xf86CompatOutput(pScrn);
+    if (!compat_output)
+	return NULL;
+    return compat_output->crtc;
+}
+
+static _X_INLINE RRCrtcPtr
+xf86CompatRRCrtc(ScrnInfoPtr pScrn)
+{
+    xf86CrtcPtr	compat_crtc = xf86CompatCrtc(pScrn);
+    if (!compat_crtc)
+	return NULL;
+    return compat_crtc->randr_crtc;
+}
+
+
 /*
  * Initialize xf86CrtcConfig structure
  */
diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index 1fc63c4dc..7ba09b6fe 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -805,9 +805,10 @@ xf86RandR12CreateScreenResources (ScreenPtr pScreen)
 	}
 	else
 	{
-	    xf86OutputPtr   output = config->output[config->compat_output];
+	    xf86OutputPtr   output = xf86CompatOutput(pScrn);
 
-	    if (output->conf_monitor &&
+	    if (output &&
+		output->conf_monitor &&
 		(output->conf_monitor->mon_width  > 0 &&
 		 output->conf_monitor->mon_height > 0))
 	    {
@@ -1719,10 +1720,13 @@ xf86RandR12ChangeGamma(int scrnIndex, Gamma gamma)
 {
     CARD16 *points, *red, *green, *blue;
     ScrnInfoPtr pScrn = xf86Screens[scrnIndex];
-    xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(pScrn);
-    RRCrtcPtr crtc = config->output[config->compat_output]->crtc->randr_crtc;
-    int size = max(0, crtc->gammaSize);
+    RRCrtcPtr crtc = xf86CompatRRCrtc(pScrn);
+    int size;
 
+    if (!crtc)
+	return Success;
+
+    size = max(0, crtc->gammaSize);
     if (!size)
 	return Success;