From 2e0336681fe7180401ebc7ad384bde809f3466b8 Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Tue, 17 Aug 2021 18:11:27 +0200
Subject: [PATCH] platforms/drm: consider KWIN_DRM_DEVICES for hotplugged gpus

---
 src/plugins/platforms/drm/drm_backend.cpp | 9 ++++++---
 src/plugins/platforms/drm/drm_backend.h   | 1 +
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/plugins/platforms/drm/drm_backend.cpp b/src/plugins/platforms/drm/drm_backend.cpp
index 669880447d..31c6b0b066 100644
--- a/src/plugins/platforms/drm/drm_backend.cpp
+++ b/src/plugins/platforms/drm/drm_backend.cpp
@@ -66,6 +66,7 @@ DrmBackend::DrmBackend(QObject *parent)
     , m_udev(new Udev)
     , m_udevMonitor(m_udev->monitor())
     , m_session(Session::create(this))
+    , m_explicitGpus(qEnvironmentVariable("KWIN_DRM_DEVICES").split(':', Qt::SkipEmptyParts))
     , m_dpmsFilter()
 {
     setSupportsGammaControl(true);
@@ -195,9 +196,8 @@ bool DrmBackend::initialize()
     connect(session(), &Session::activeChanged, this, &DrmBackend::activate);
     connect(session(), &Session::awoke, this, &DrmBackend::turnOutputsOn);
 
-    const QStringList explicitGpus = qEnvironmentVariable("KWIN_DRM_DEVICES").split(':', Qt::SkipEmptyParts);
-    if (!explicitGpus.isEmpty()) {
-        for (const QString &fileName : explicitGpus) {
+    if (!m_explicitGpus.isEmpty()) {
+        for (const QString &fileName : m_explicitGpus) {
             addGpu(fileName);
         }
     } else {
@@ -254,6 +254,9 @@ void DrmBackend::handleUdevEvent()
         }
 
         if (device->action() == QStringLiteral("add")) {
+            if (!m_explicitGpus.isEmpty() && !m_explicitGpus.contains(device->devNode())) {
+                continue;
+            }
             qCDebug(KWIN_DRM) << "New gpu found:" << device->devNode();
             if (addGpu(device->devNode())) {
                 updateOutputs();
diff --git a/src/plugins/platforms/drm/drm_backend.h b/src/plugins/platforms/drm/drm_backend.h
index f26c7bf791..2b844cbf53 100644
--- a/src/plugins/platforms/drm/drm_backend.h
+++ b/src/plugins/platforms/drm/drm_backend.h
@@ -105,6 +105,7 @@ private:
     DrmVirtualOutput *m_placeHolderOutput = nullptr;
 
     bool m_active = false;
+    const QStringList m_explicitGpus;
     QVector<DrmGpu*> m_gpus;
     QScopedPointer<DpmsInputEventFilter> m_dpmsFilter;
 };