backends/drm: don't take crtcs from dpms disabled outputs

Fixes a crash I have with dpms + suspend, which was caused by the udev
event for updating outputs being called before the output got enabled
again. When DrmGpu::updateOutputs got called it removed the crtc from
the inactive output and then disabled the output afterwards. Instead,
only remove crtcs if an output is really disabled.
This also allows to generalize the logic for lease outputs, and could
in the future allow for faster dpms on/off switching.

src/backends/drm/drm_gpu.cpp

@@ -268,6 +268,8 @@ bool DrmGpu::updateOutputs()
                 qCDebug(KWIN_DRM, "New %soutput on GPU %s: %s", conn->isNonDesktop() ? "non-desktop " : "", qPrintable(m_devNode), qPrintable(conn->modelName()));
                 m_pipelines << conn->pipeline();
                 if (conn->isNonDesktop()) {
+                    conn->pipeline()->pending.active = false;
+                    conn->pipeline()->applyPendingChanges();
                     auto leaseOutput = new DrmLeaseOutput(conn->pipeline(), m_leaseDevice);
                     m_leaseOutputs << leaseOutput;
                 } else {
@@ -311,6 +313,7 @@ bool DrmGpu::updateOutputs()
         for (const auto &pipeline : qAsConst(m_pipelines)) {
             pipeline->applyPendingChanges();
             if (!pipeline->pending.crtc && pipeline->output()) {
+                pipeline->pending.enabled = false;
                 pipeline->output()->setEnabled(false);
             }
         }
@@ -335,35 +338,28 @@ bool DrmGpu::checkCrtcAssignment(QVector<DrmConnector*> connectors, QVector<DrmC
             qCWarning(KWIN_DRM) << "disabling connector" << conn->modelName() << "without a crtc";
             conn->pipeline()->pending.crtc = nullptr;
         }
-        // non-desktop outputs need to be tested when they would be enabled so that they can be used if leased
+        // pipelines that are enabled but not active need to be activated for the test
-        QVector<DrmPipeline*> leasePipelines;
+        QVector<DrmPipeline*> inactivePipelines;
-        for (const auto &output : qAsConst(m_leaseOutputs)) {
+        for (const auto &pipeline : qAsConst(m_pipelines)) {
-            if (!output->lease()) {
+            if (!pipeline->pending.active) {
-                output->pipeline()->pending.active = true;
+                pipeline->pending.active = true;
-                leasePipelines << output->pipeline();
+                inactivePipelines << pipeline;
             }
         }
         const auto unused = unusedObjects();
         bool test = DrmPipeline::commitPipelines(m_pipelines, DrmPipeline::CommitMode::Test, unused);
-        if (!leasePipelines.isEmpty() && test) {
+        // disable inactive pipelines again
-            // non-desktop outputs should be disabled for normal usage
+        for (const auto &pipeline : qAsConst(inactivePipelines)) {
-            for (const auto &pipeline : qAsConst(leasePipelines)) {
+            pipeline->pending.active = false;
-                pipeline->pending.active = false;
-            }
-            bool ret = DrmPipeline::commitPipelines(m_pipelines, DrmPipeline::CommitMode::Test, unused);
-            if (ret) {
-                for (const auto &pipeline : qAsConst(leasePipelines)) {
-                    pipeline->applyPendingChanges();
-                }
-            }
-            return ret;
-        } else {
-            return test;
         }
+        if (!inactivePipelines.isEmpty() && test) {
+            test = DrmPipeline::commitPipelines(m_pipelines, DrmPipeline::CommitMode::Test, unused);
+        }
+        return test;
     }
     auto connector = connectors.takeFirst();
     auto pipeline = connector->pipeline();
-    if (const auto &output = pipeline->output(); output && !pipeline->pending.active) {
+    if (!pipeline->pending.enabled) {
         // disabled pipelines don't need CRTCs
         pipeline->pending.crtc = nullptr;
         return checkCrtcAssignment(connectors, crtcs);

src/backends/drm/drm_output.cpp

@@ -453,6 +453,7 @@ bool DrmOutput::queueChanges(const WaylandOutputConfig &config)
     m_pipeline->pending.overscan = props->overscan;
     m_pipeline->pending.rgbRange = props->rgbRange;
     m_pipeline->pending.transformation = DrmPlane::Transformation::Rotate0;
+    m_pipeline->pending.enabled = props->enabled;
     return true;
 }
 

src/backends/drm/drm_pipeline.h

@@ -92,7 +92,8 @@ public:
 
     struct State {
         DrmCrtc *crtc = nullptr;
-        bool active = true;
+        bool active = true; // whether or not the pipeline should be currently used
+        bool enabled = true;// whether or not the pipeline needs a crtc
         int modeIndex = 0;
         uint32_t overscan = 0;
         AbstractWaylandOutput::RgbRange rgbRange = AbstractWaylandOutput::RgbRange::Automatic;