platforms/drm: use gbm with NVidia driver 495+

(cherry picked from commit dc56b03d)

src/plugins/platforms/drm/drm_gpu.cpp

@@ -74,7 +74,14 @@ DrmGpu::DrmGpu(DrmBackend *backend, const QString &devNode, int fd, dev_t device
 
     // find out if this GPU is using the NVidia proprietary driver
     DrmScopedPointer<drmVersion> version(drmGetVersion(fd));
-    m_useEglStreams = strstr(version->name, "nvidia-drm");
+    m_isNVidia = strstr(version->name, "nvidia-drm");
+    m_useEglStreams = m_isNVidia;
+#if HAVE_GBM
+    m_gbmDevice = gbm_create_device(m_fd);
+    if (m_gbmDevice) {
+        m_useEglStreams = m_isNVidia && strcmp(gbm_device_get_backend_name(m_gbmDevice), "nvidia") != 0;
+    }
+#endif
 
     m_socketNotifier = new QSocketNotifier(fd, QSocketNotifier::Read, this);
     connect(m_socketNotifier, &QSocketNotifier::activated, this, &DrmGpu::dispatchEvents);
@@ -551,4 +558,9 @@ bool DrmGpu::isFormatSupported(uint32_t drmFormat) const
     }
 }
 
+bool DrmGpu::isNVidia() const
+{
+    return m_isNVidia;
+}
+
 }

src/plugins/platforms/drm/drm_gpu.h

@@ -94,6 +94,7 @@ public:
     bool addFB2ModifiersSupported() const {
         return m_addFB2ModifiersSupported;
     }
+    bool isNVidia() const;
 
     void waitIdle();
     DrmBackend *platform() const;
@@ -131,6 +132,7 @@ private:
     const dev_t m_deviceId;
     bool m_atomicModeSetting;
     bool m_useEglStreams;
+    bool m_isNVidia;
     gbm_device* m_gbmDevice;
     EGLDisplay m_eglDisplay = EGL_NO_DISPLAY;
     clockid_t m_presentationClock;

src/plugins/platforms/drm/drm_object_plane.cpp

@@ -73,7 +73,10 @@ bool DrmPlane::init()
         checkSupport(5, Transformation::ReflectY);
 
         // read formats from blob if available and if modifiers are supported, and from the plane object if not
-        if (auto formatProp = getProp(PropertyIndex::In_Formats); formatProp && gpu()->addFB2ModifiersSupported() && qEnvironmentVariableIntValue("KWIN_DRM_USE_MODIFIERS") == 1) {
+        bool modifiersEnvSet = false;
+        bool modifiersEnv = qEnvironmentVariableIntValue("KWIN_DRM_USE_MODIFIERS", &modifiersEnvSet) != 0;
+        bool allowModifiers = (gpu()->isNVidia() && !modifiersEnvSet) || (modifiersEnvSet && modifiersEnv);
+        if (auto formatProp = getProp(PropertyIndex::In_Formats); formatProp && gpu()->addFB2ModifiersSupported() && allowModifiers) {
             DrmScopedPointer<drmModePropertyBlobRes> propertyBlob(drmModeGetPropertyBlob(gpu()->fd(), formatProp->current()));
             if (propertyBlob && propertyBlob->data) {
                 auto blob = static_cast<drm_format_modifier_blob*>(propertyBlob->data);

src/plugins/platforms/drm/egl_gbm_backend.cpp

@@ -88,14 +88,12 @@ bool EglGbmBackend::initializeEgl()
             return false;
         }
 
-        auto device = gbm_create_device(m_gpu->fd());
-        if (!device) {
+        if (!m_gpu->gbmDevice()) {
             setFailed("Could not create gbm device");
             return false;
         }
-        m_gpu->setGbmDevice(device);
 
-        display = eglGetPlatformDisplayEXT(platform, device, nullptr);
+        display = eglGetPlatformDisplayEXT(platform, m_gpu->gbmDevice(), nullptr);
         m_gpu->setEglDisplay(display);
     }