xrandrprovider: Do not use separate lists for unbound / source / offload slaves

A single provider can be both a offload and source slave at the same time,
the use of seperate lists breaks in this case e.g. :

xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x7b cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 3 outputs: 2 associated providers: 0 name:modesetting
Provider 1: id: 0x46 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 2 outputs: 5 associated providers: 0 name:modesetting

xrandr --setprovideroutputsource 1 0x7b
xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x7b cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 3 outputs: 2 associated providers: 1 name:modesetting
Provider 1: id: 0x46 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 2 outputs: 5 associated providers: 1 name:modesetting

xrandr --setprovideroffloadsink 1 0x7b
xrandr --listproviders
Providers: number : 3
Provider 0: id: 0x7b cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 3 outputs: 2 associated providers: 2 name:modesetting
Provider 1: id: 0x46 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 2 outputs: 5 associated providers: 2 name:modesetting
Provider 2: id: 0x46 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 2 outputs: 5 associated providers: 2 name:modesetting

Not good. The problem is that the provider with id 0x46 now is on both
the output_slave_list and the offload_slave_list of the master screen.

This commit fixes this by unifying all 3 lists into a single slaves list.

Note that this does change the struct _Screen definition, so this is an ABI
break. I do not expect any of the drivers to actually use the removed / changed
fields so a recompile should suffice.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

11 files changed, 104 insertions, 108 deletions

diff --git a/dix/dispatch.c b/dix/dispatch.c
index 86124c683..8a7eff712 100644
--- a/dix/dispatch.c
+++ b/dix/dispatch.c
@@ -3789,9 +3789,7 @@ static int init_screen(ScreenPtr pScreen, int i, Bool gpu)
     pScreen->CreateScreenResources = 0;
 
     xorg_list_init(&pScreen->pixmap_dirty_list);
-    xorg_list_init(&pScreen->unattached_list);
-    xorg_list_init(&pScreen->output_slave_list);
-    xorg_list_init(&pScreen->offload_slave_list);
+    xorg_list_init(&pScreen->slave_list);
 
     /*
      * This loop gets run once for every Screen that gets added,
@@ -3950,7 +3948,7 @@ AttachUnboundGPU(ScreenPtr pScreen, ScreenPtr new)
 {
     assert(new->isGPU);
     assert(!new->current_master);
-    xorg_list_add(&new->unattached_head, &pScreen->unattached_list);
+    xorg_list_add(&new->slave_head, &pScreen->slave_list);
     new->current_master = pScreen;
 }
 
@@ -3958,7 +3956,9 @@ void
 DetachUnboundGPU(ScreenPtr slave)
 {
     assert(slave->isGPU);
-    xorg_list_del(&slave->unattached_head);
+    assert(!slave->is_output_slave);
+    assert(!slave->is_offload_slave);
+    xorg_list_del(&slave->slave_head);
     slave->current_master = NULL;
 }
 
@@ -3966,31 +3966,35 @@ void
 AttachOutputGPU(ScreenPtr pScreen, ScreenPtr new)
 {
     assert(new->isGPU);
-    xorg_list_add(&new->output_head, &pScreen->output_slave_list);
-    new->current_master = pScreen;
+    assert(!new->is_output_slave);
+    assert(new->current_master == pScreen);
+    new->is_output_slave = TRUE;
+    new->current_master->output_slaves++;
 }
 
 void
 DetachOutputGPU(ScreenPtr slave)
 {
     assert(slave->isGPU);
-    xorg_list_del(&slave->output_head);
-    slave->current_master = NULL;
+    assert(slave->is_output_slave);
+    slave->current_master->output_slaves--;
+    slave->is_output_slave = FALSE;
 }
 
 void
 AttachOffloadGPU(ScreenPtr pScreen, ScreenPtr new)
 {
     assert(new->isGPU);
-    xorg_list_add(&new->offload_head, &pScreen->offload_slave_list);
-    new->current_master = pScreen;
+    assert(!new->is_offload_slave);
+    assert(new->current_master == pScreen);
+    new->is_offload_slave = TRUE;
 }
 
 void
 DetachOffloadGPU(ScreenPtr slave)
 {
     assert(slave->isGPU);
-    xorg_list_del(&slave->offload_head);
-    slave->current_master = NULL;
+    assert(slave->is_offload_slave);
+    slave->is_offload_slave = FALSE;
 }
 
diff --git a/hw/xfree86/dri2/dri2.c b/hw/xfree86/dri2/dri2.c
index f80599fb7..2165603d9 100644
--- a/hw/xfree86/dri2/dri2.c
+++ b/hw/xfree86/dri2/dri2.c
@@ -186,12 +186,15 @@ static ScreenPtr
 GetScreenPrime(ScreenPtr master, int prime_id)
 {
     ScreenPtr slave;
-    if (prime_id == 0 || xorg_list_is_empty(&master->offload_slave_list)) {
+    if (prime_id == 0) {
         return master;
     }
-    xorg_list_for_each_entry(slave, &master->offload_slave_list, offload_head) {
+    xorg_list_for_each_entry(slave, &master->slave_list, slave_head) {
         DRI2ScreenPtr ds;
 
+        if (!slave->is_offload_slave)
+            continue;
+
         ds = DRI2GetScreen(slave);
         if (ds == NULL)
             continue;
diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index 60d22543e..4a21766e0 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -1836,10 +1836,7 @@ xf86RandR14ProviderSetOutputSource(ScreenPtr pScreen,
 {
     if (!source_provider) {
         if (provider->output_source) {
-            ScreenPtr cmScreen = pScreen->current_master;
-
             xf86DetachOutputGPU(pScreen);
-            AttachUnboundGPU(cmScreen, pScreen);
         }
         provider->output_source = NULL;
         return TRUE;
@@ -1850,7 +1847,6 @@ xf86RandR14ProviderSetOutputSource(ScreenPtr pScreen,
 
     SetRootClip(source_provider->pScreen, ROOT_CLIP_NONE);
 
-    DetachUnboundGPU(pScreen);
     AttachOutputGPU(source_provider->pScreen, pScreen);
 
     provider->output_source = source_provider;
@@ -1865,9 +1861,7 @@ xf86RandR14ProviderSetOffloadSink(ScreenPtr pScreen,
 {
     if (!sink_provider) {
         if (provider->offload_sink) {
-            ScreenPtr cmScreen = pScreen->current_master;
             xf86DetachOutputGPU(pScreen);
-            AttachUnboundGPU(cmScreen, pScreen);
         }
 
         provider->offload_sink = NULL;
@@ -1877,7 +1871,6 @@ xf86RandR14ProviderSetOffloadSink(ScreenPtr pScreen,
     if (provider->offload_sink == sink_provider)
         return TRUE;
 
-    DetachUnboundGPU(pScreen);
     AttachOffloadGPU(sink_provider->pScreen, pScreen);
 
     provider->offload_sink = sink_provider;
@@ -1956,12 +1949,12 @@ xf86RandR14ProviderDestroy(ScreenPtr screen, RRProviderPtr provider)
             config->randr_provider->offload_sink = NULL;
             RRSetChanged(screen);
         }
-        else if (config->randr_provider->output_source) {
+        if (config->randr_provider->output_source) {
             xf86DetachOutputGPU(screen);
             config->randr_provider->output_source = NULL;
             RRSetChanged(screen);
         }
-        else if (screen->current_master)
+        if (screen->current_master)
             DetachUnboundGPU(screen);
     }
     config->randr_provider = NULL;
diff --git a/include/scrnintstr.h b/include/scrnintstr.h
index 2e617c466..63ef55c10 100644
--- a/include/scrnintstr.h
+++ b/include/scrnintstr.h
@@ -590,13 +590,14 @@ typedef struct _Screen {
 
     Bool isGPU;
 
-    struct xorg_list unattached_list;
-    struct xorg_list unattached_head;
-
+    /* Info on this screen's slaves (if any) */
+    struct xorg_list slave_list;
+    struct xorg_list slave_head;
+    int output_slaves;
+    /* Info for when this screen is a slave */
     ScreenPtr current_master;
-
-    struct xorg_list output_slave_list;
-    struct xorg_list output_head;
+    Bool is_output_slave;
+    Bool is_offload_slave;
 
     SharePixmapBackingProcPtr SharePixmapBacking;
     SetSharedPixmapBackingProcPtr SetSharedPixmapBacking;
@@ -605,8 +606,6 @@ typedef struct _Screen {
     StopPixmapTrackingProcPtr StopPixmapTracking;
 
     struct xorg_list pixmap_dirty_list;
-    struct xorg_list offload_slave_list;
-    struct xorg_list offload_head;
 
     ReplaceScanoutPixmapProcPtr ReplaceScanoutPixmap;
     XYToWindowProcPtr XYToWindow;
diff --git a/present/present.c b/present/present.c
index cebd2f786..521083287 100644
--- a/present/present.c
+++ b/present/present.c
@@ -145,7 +145,7 @@ present_check_flip(RRCrtcPtr    crtc,
         return FALSE;
 
     /* Fail to flip if we have slave outputs */
-    if (!xorg_list_is_empty(&screen->output_slave_list))
+    if (screen->output_slaves)
         return FALSE;
 
     /* Make sure the window hasn't been redirected with Composite */
diff --git a/randr/randr.c b/randr/randr.c
index 3aabb1981..95ed7e5e6 100644
--- a/randr/randr.c
+++ b/randr/randr.c
@@ -483,7 +483,10 @@ TellChanged(WindowPtr pWin, void *value)
                     RRDeliverCrtcEvent(client, pWin, crtc);
             }
 
-            xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
+            xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
+                if (!iter->is_output_slave)
+                    continue;
+
                 pSlaveScrPriv = rrGetScrPriv(iter);
                 for (i = 0; i < pSlaveScrPriv->numCrtcs; i++) {
                     RRCrtcPtr crtc = pSlaveScrPriv->crtcs[i];
@@ -502,7 +505,10 @@ TellChanged(WindowPtr pWin, void *value)
                     RRDeliverOutputEvent(client, pWin, output);
             }
 
-            xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
+            xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
+                if (!iter->is_output_slave)
+                    continue;
+
                 pSlaveScrPriv = rrGetScrPriv(iter);
                 for (i = 0; i < pSlaveScrPriv->numOutputs; i++) {
                     RROutputPtr output = pSlaveScrPriv->outputs[i];
@@ -514,17 +520,7 @@ TellChanged(WindowPtr pWin, void *value)
         }
 
         if (pRREvent->mask & RRProviderChangeNotifyMask) {
-            xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
-                pSlaveScrPriv = rrGetScrPriv(iter);
-                if (pSlaveScrPriv->provider->changed)
-                    RRDeliverProviderEvent(client, pWin, pSlaveScrPriv->provider);
-            }
-            xorg_list_for_each_entry(iter, &pScreen->offload_slave_list, offload_head) {
-                pSlaveScrPriv = rrGetScrPriv(iter);
-                if (pSlaveScrPriv->provider->changed)
-                    RRDeliverProviderEvent(client, pWin, pSlaveScrPriv->provider);
-            }
-            xorg_list_for_each_entry(iter, &pScreen->unattached_list, unattached_head) {
+            xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
                 pSlaveScrPriv = rrGetScrPriv(iter);
                 if (pSlaveScrPriv->provider->changed)
                     RRDeliverProviderEvent(client, pWin, pSlaveScrPriv->provider);
@@ -602,21 +598,15 @@ RRTellChanged(ScreenPtr pScreen)
         for (i = 0; i < pScrPriv->numCrtcs; i++)
             pScrPriv->crtcs[i]->changed = FALSE;
 
-        xorg_list_for_each_entry(iter, &master->output_slave_list, output_head) {
-            pSlaveScrPriv = rrGetScrPriv(iter);
-            pSlaveScrPriv->provider->changed = FALSE;
-            for (i = 0; i < pSlaveScrPriv->numOutputs; i++)
-                pSlaveScrPriv->outputs[i]->changed = FALSE;
-            for (i = 0; i < pSlaveScrPriv->numCrtcs; i++)
-                pSlaveScrPriv->crtcs[i]->changed = FALSE;
-        }
-        xorg_list_for_each_entry(iter, &master->offload_slave_list, offload_head) {
-            pSlaveScrPriv = rrGetScrPriv(iter);
-            pSlaveScrPriv->provider->changed = FALSE;
-        }
-        xorg_list_for_each_entry(iter, &master->unattached_list, unattached_head) {
+        xorg_list_for_each_entry(iter, &master->slave_list, slave_head) {
             pSlaveScrPriv = rrGetScrPriv(iter);
             pSlaveScrPriv->provider->changed = FALSE;
+            if (iter->is_output_slave) {
+                for (i = 0; i < pSlaveScrPriv->numOutputs; i++)
+                    pSlaveScrPriv->outputs[i]->changed = FALSE;
+                for (i = 0; i < pSlaveScrPriv->numCrtcs; i++)
+                    pSlaveScrPriv->crtcs[i]->changed = FALSE;
+            }
         }
 
         if (mastersp->layoutChanged) {
diff --git a/randr/rrcrtc.c b/randr/rrcrtc.c
index 54471332d..ea91ab703 100644
--- a/randr/rrcrtc.c
+++ b/randr/rrcrtc.c
@@ -526,8 +526,12 @@ rrCheckPixmapBounding(ScreenPtr pScreen,
         RegionUnion(&total_region, &total_region, &new_crtc_region);
     }
 
-    xorg_list_for_each_entry(slave, &pScreen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(slave, &pScreen->slave_list, slave_head) {
         rrScrPrivPtr    slave_priv = rrGetScrPriv(slave);
+
+        if (!slave->is_output_slave)
+            continue;
+
         for (c = 0; c < slave_priv->numCrtcs; c++) {
             RRCrtcPtr slave_crtc = slave_priv->crtcs[c];
 
@@ -1700,7 +1704,10 @@ RRConstrainCursorHarder(DeviceIntPtr pDev, ScreenPtr pScreen, int mode, int *x,
     if (ret == TRUE)
         return;
 
-    xorg_list_for_each_entry(slave, &pScreen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(slave, &pScreen->slave_list, slave_head) {
+        if (!slave->is_output_slave)
+            continue;
+
         ret = check_all_screen_crtcs(slave, x, y);
         if (ret == TRUE)
             return;
@@ -1711,7 +1718,10 @@ RRConstrainCursorHarder(DeviceIntPtr pDev, ScreenPtr pScreen, int mode, int *x,
     if (ret == TRUE)
         return;
 
-    xorg_list_for_each_entry(slave, &pScreen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(slave, &pScreen->slave_list, slave_head) {
+        if (!slave->is_output_slave)
+            continue;
+
         ret = constrain_all_screen_crtcs(pDev, slave, x, y);
         if (ret == TRUE)
             return;
diff --git a/randr/rrmonitor.c b/randr/rrmonitor.c
index ba310eaa4..3f6e03e7d 100644
--- a/randr/rrmonitor.c
+++ b/randr/rrmonitor.c
@@ -202,8 +202,12 @@ RRMonitorInitList(ScreenPtr screen, RRMonitorListPtr mon_list, Bool get_active)
 
     /* Count the number of crtcs in this and any slave screens */
     numCrtcs = pScrPriv->numCrtcs;
-    xorg_list_for_each_entry(slave, &screen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(slave, &screen->slave_list, slave_head) {
         rrScrPrivPtr pSlavePriv;
+
+        if (!slave->is_output_slave)
+            continue;
+
         pSlavePriv = rrGetScrPriv(slave);
         numCrtcs += pSlavePriv->numCrtcs;
     }
@@ -220,8 +224,12 @@ RRMonitorInitList(ScreenPtr screen, RRMonitorListPtr mon_list, Bool get_active)
             mon_list->server_crtc[c] = pScrPriv->crtcs[sc];
     }
 
-    xorg_list_for_each_entry(slave, &screen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(slave, &screen->slave_list, slave_head) {
         rrScrPrivPtr pSlavePriv;
+
+        if (!slave->is_output_slave)
+            continue;
+
         pSlavePriv = rrGetScrPriv(slave);
         for (sc = 0; sc < pSlavePriv->numCrtcs; sc++, c++) {
             if (pSlavePriv->crtcs[sc]->mode != NULL)
@@ -471,7 +479,10 @@ RRMonitorAdd(ClientPtr client, ScreenPtr screen, RRMonitorPtr monitor)
         return BadValue;
     }
 
-    xorg_list_for_each_entry(slave, &screen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(slave, &screen->slave_list, slave_head) {
+        if (!slave->is_output_slave)
+            continue;
+
         if (RRMonitorMatchesOutputName(slave, monitor->name)) {
             client->errorValue = monitor->name;
             return BadValue;
diff --git a/randr/rroutput.c b/randr/rroutput.c
index 686ae49a6..a8efec409 100644
--- a/randr/rroutput.c
+++ b/randr/rroutput.c
@@ -570,12 +570,10 @@ ProcRRSetOutputPrimary(ClientPtr client)
         RRSetPrimaryOutput(pWin->drawable.pScreen, pScrPriv, output);
 
         xorg_list_for_each_entry(slave,
-                                 &pWin->drawable.pScreen->output_slave_list,
-                                 output_head) {
-            rrScrPrivPtr pSlavePriv;
-            pSlavePriv = rrGetScrPriv(slave);
-
-            RRSetPrimaryOutput(slave, pSlavePriv, output);
+                                 &pWin->drawable.pScreen->slave_list,
+                                 slave_head) {
+            if (slave->is_output_slave)
+                RRSetPrimaryOutput(slave, rrGetScrPriv(slave), output);
         }
     }
 
diff --git a/randr/rrprovider.c b/randr/rrprovider.c
index 5329f410b..8ef47260c 100644
--- a/randr/rrprovider.c
+++ b/randr/rrprovider.c
@@ -72,15 +72,7 @@ ProcRRGetProviders (ClientPtr client)
 
     if (pScrPriv->provider)
         total_providers++;
-    xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
-        pScrPriv = rrGetScrPriv(iter);
-        total_providers += pScrPriv->provider ? 1 : 0;
-    }
-    xorg_list_for_each_entry(iter, &pScreen->offload_slave_list, offload_head) {
-        pScrPriv = rrGetScrPriv(iter);
-        total_providers += pScrPriv->provider ? 1 : 0;
-    }
-    xorg_list_for_each_entry(iter, &pScreen->unattached_list, unattached_head) {
+    xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
         pScrPriv = rrGetScrPriv(iter);
         total_providers += pScrPriv->provider ? 1 : 0;
     }
@@ -116,13 +108,7 @@ ProcRRGetProviders (ClientPtr client)
 
         providers = (RRProvider *)extra;
         ADD_PROVIDER(pScreen);
-        xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
-            ADD_PROVIDER(iter);
-        }
-        xorg_list_for_each_entry(iter, &pScreen->offload_slave_list, offload_head) {
-            ADD_PROVIDER(iter);
-        }
-        xorg_list_for_each_entry(iter, &pScreen->unattached_list, unattached_head) {
+        xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
             ADD_PROVIDER(iter);
         }
     }
@@ -182,12 +168,13 @@ ProcRRGetProviderInfo (ClientPtr client)
     /* count associated providers */
     if (provider->offload_sink)
         rep.nAssociatedProviders++;
-    if (provider->output_source)
-        rep.nAssociatedProviders++;
-    xorg_list_for_each_entry(provscreen, &pScreen->output_slave_list, output_head)
-        rep.nAssociatedProviders++;
-    xorg_list_for_each_entry(provscreen, &pScreen->offload_slave_list, offload_head)
+    if (provider->output_source &&
+            provider->output_source != provider->offload_sink)
         rep.nAssociatedProviders++;
+    xorg_list_for_each_entry(provscreen, &pScreen->slave_list, slave_head) {
+        if (provscreen->is_output_slave || provscreen->is_offload_slave)
+            rep.nAssociatedProviders++;
+    }
 
     rep.length = (pScrPriv->numCrtcs + pScrPriv->numOutputs +
                   (rep.nAssociatedProviders * 2) + bytes_to_int32(rep.nameLength));
@@ -237,27 +224,22 @@ ProcRRGetProviderInfo (ClientPtr client)
             swapl(&prov_cap[i]);
         i++;
     }
-    xorg_list_for_each_entry(provscreen, &pScreen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(provscreen, &pScreen->slave_list, slave_head) {
+        if (!provscreen->is_output_slave && !provscreen->is_offload_slave)
+            continue;
         pScrProvPriv = rrGetScrPriv(provscreen);
         providers[i] = pScrProvPriv->provider->id;
         if (client->swapped)
             swapl(&providers[i]);
-        prov_cap[i] = RR_Capability_SinkOutput;
+        prov_cap[i] = 0;
+        if (provscreen->is_output_slave)
+            prov_cap[i] |= RR_Capability_SinkOutput;
+        if (provscreen->is_offload_slave)
+            prov_cap[i] |= RR_Capability_SourceOffload;
         if (client->swapped)
             swapl(&prov_cap[i]);
         i++;
     }
-    xorg_list_for_each_entry(provscreen, &pScreen->offload_slave_list, offload_head) {
-        pScrProvPriv = rrGetScrPriv(provscreen);
-        providers[i] = pScrProvPriv->provider->id;
-        if (client->swapped)
-            swapl(&providers[i]);
-        prov_cap[i] = RR_Capability_SourceOffload;
-        if (client->swapped)
-            swapl(&prov_cap[i]);
-        i++;
-    }
-
 
     memcpy(name, provider->name, rep.nameLength);
     if (client->swapped) {
diff --git a/randr/rrscreen.c b/randr/rrscreen.c
index b5e2090d9..d6c499580 100644
--- a/randr/rrscreen.c
+++ b/randr/rrscreen.c
@@ -394,7 +394,10 @@ rrGetMultiScreenResources(ClientPtr client, Bool query, ScreenPtr pScreen)
 
     update_totals(pScreen, pScrPriv);
 
-    xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
+        if (!iter->is_output_slave)
+            continue;
+
         pScrPriv = rrGetScrPriv(iter);
 
         if (query)
@@ -450,7 +453,10 @@ rrGetMultiScreenResources(ClientPtr client, Bool query, ScreenPtr pScreen)
     }
     update_arrays(pScreen, pScrPriv, primary_crtc, has_primary);
 
-    xorg_list_for_each_entry(iter, &pScreen->output_slave_list, output_head) {
+    xorg_list_for_each_entry(iter, &pScreen->slave_list, slave_head) {
+        if (!iter->is_output_slave)
+            continue;
+
         pScrPriv = rrGetScrPriv(iter);
 
         update_arrays(iter, pScrPriv, primary_crtc, has_primary);
@@ -503,7 +509,7 @@ rrGetScreenResources(ClientPtr client, Bool query)
         if (!RRGetInfo(pScreen, query))
             return BadAlloc;
 
-    if (!xorg_list_is_empty(&pScreen->output_slave_list))
+    if (pScreen->output_slaves)
         return rrGetMultiScreenResources(client, query, pScreen);
 
     if (!pScrPriv) {