[platforms/drm] Pass ownership of gbm_device to Platform

Just like 4e7392b9075d78066218e55250e266fddaa03a7c:
the ownership of the gbm_device must be passed to the Platform as
the ownership of the EGLDisplay is also passed to the Platform and
we may not destroy the gbm_device for an EGLDisplay we are still using.

With this change I could restart the OpenGL compositor successfully
and switch from OpenGL 3.1 to OpenGL 2 without a crash or rendering
issues.

plugins/platforms/drm/drm_backend.cpp

@@ -30,6 +30,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "wayland_server.h"
 #if HAVE_GBM
 #include "egl_gbm_backend.h"
+#include <gbm.h>
 #endif
 // KWayland
 #include <KWayland/Server/seat_interface.h>
@@ -73,6 +74,11 @@ DrmBackend::DrmBackend(QObject *parent)
 
 DrmBackend::~DrmBackend()
 {
+#if HAVE_GBM
+    if (m_gbmDevice) {
+        gbm_device_destroy(m_gbmDevice);
+    }
+#endif
     if (m_fd >= 0) {
         // wait for pageflips
         while (m_pageFlipsPending != 0) {

plugins/platforms/drm/drm_backend.h

@@ -33,6 +33,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <xf86drmMode.h>
 
 struct gbm_bo;
+struct gbm_device;
 struct gbm_surface;
 
 namespace KWayland
@@ -89,6 +90,13 @@ public:
     void outputWentOff();
     void checkOutputsAreOn();
 
+    void setGbmDevice(gbm_device *device) {
+        m_gbmDevice = device;
+    }
+    gbm_device *gbmDevice() const {
+        return m_gbmDevice;
+    }
+
 public Q_SLOTS:
     void turnOutputsOn();
 
@@ -129,6 +137,7 @@ private:
     QVector<DrmBuffer*> m_buffers;
     QScopedPointer<DpmsInputEventFilter> m_dpmsFilter;
     KWayland::Server::OutputManagementInterface *m_outputManagement = nullptr;
+    gbm_device *m_gbmDevice = nullptr;
 };
 
 

plugins/platforms/drm/egl_gbm_backend.cpp

@@ -64,9 +64,6 @@ EglGbmBackend::~EglGbmBackend()
 {
     // TODO: cleanup front buffer?
     cleanup();
-    if (m_device) {
-        gbm_device_destroy(m_device);
-    }
 }
 
 void EglGbmBackend::cleanupSurfaces()
@@ -101,13 +98,14 @@ bool EglGbmBackend::initializeEgl()
             return false;
         }
 
-        m_device = gbm_create_device(m_backend->fd());
-        if (!m_device) {
+        auto device = gbm_create_device(m_backend->fd());
+        if (!device) {
             setFailed("Could not create gbm device");
             return false;
         }
+        m_backend->setGbmDevice(device);
 
-        display = eglGetPlatformDisplayEXT(EGL_PLATFORM_GBM_MESA, m_device, nullptr);
+        display = eglGetPlatformDisplayEXT(EGL_PLATFORM_GBM_MESA, device, nullptr);
     }
 
     if (display == EGL_NO_DISPLAY)
@@ -158,7 +156,7 @@ void EglGbmBackend::createOutput(DrmOutput *drmOutput)
 {
     Output o;
     o.output = drmOutput;
-    o.gbmSurface = gbm_surface_create(m_device, drmOutput->size().width(), drmOutput->size().height(),
+    o.gbmSurface = gbm_surface_create(m_backend->gbmDevice(), drmOutput->size().width(), drmOutput->size().height(),
                                         GBM_FORMAT_XRGB8888, GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
     if (!o.gbmSurface) {
         qCCritical(KWIN_DRM) << "Create gbm surface failed";

plugins/platforms/drm/egl_gbm_backend.h

@@ -22,7 +22,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "abstract_egl_backend.h"
 #include "scene_opengl.h"
 
-struct gbm_device;
 struct gbm_surface;
 
 namespace KWin
@@ -74,7 +73,6 @@ private:
     void cleanupOutput(const Output &output);
     void createOutput(DrmOutput *output);
     DrmBackend *m_backend;
-    gbm_device *m_device = nullptr;
     QVector<Output> m_outputs;
     friend class EglGbmTexture;
 };