eglfs: Forward nativeRes.ForInteg.() to backends

Expose the fd from eglfs_kms. More exposed bits will follow
later on.

[ChangeLog][Platform Specific Changes][eglfs] The DRM+GBM backend
now exposes the DRM/GBM device handle under the key "dri_fd",
queriable via nativeResourceForIntegration().

Task-number: QTBUG-63088
Change-Id: Iac95393c115bb83d1f65cb4a7acc0ea3e7d3e68f
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

src/plugins/platforms/eglfs/api/qeglfsdeviceintegration.cpp

@@ -357,6 +357,12 @@ QFunctionPointer QEglFSDeviceIntegration::platformFunction(const QByteArray &fun
     return nullptr;
 }
 
+void *QEglFSDeviceIntegration::nativeResourceForIntegration(const QByteArray &name)
+{
+    Q_UNUSED(name);
+    return nullptr;
+}
+
 void *QEglFSDeviceIntegration::wlDisplay() const
 {
     return Q_NULLPTR;

src/plugins/platforms/eglfs/api/qeglfsdeviceintegration_p.h

@@ -104,6 +104,7 @@ public:
     virtual bool supportsPBuffers() const;
     virtual bool supportsSurfacelessContexts() const;
     virtual QFunctionPointer platformFunction(const QByteArray &function) const;
+    virtual void *nativeResourceForIntegration(const QByteArray &name);
 
     virtual void *wlDisplay() const;
 

src/plugins/platforms/eglfs/api/qeglfsintegration.cpp

@@ -324,6 +324,7 @@ void *QEglFSIntegration::nativeResourceForIntegration(const QByteArray &resource
         result = qt_egl_device_integration()->wlDisplay();
         break;
     default:
+        result = qt_egl_device_integration()->nativeResourceForIntegration(resource);
         break;
     }
 

src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsintegration.cpp

@@ -133,6 +133,14 @@ bool QEglFSKmsIntegration::supportsPBuffers() const
     return m_screenConfig->supportsPBuffers();
 }
 
+void *QEglFSKmsIntegration::nativeResourceForIntegration(const QByteArray &name)
+{
+    if (name == QByteArrayLiteral("dri_fd") && m_device)
+        return (void *) (qintptr) m_device->fd();
+
+    return nullptr;
+}
+
 QKmsDevice *QEglFSKmsIntegration::device() const
 {
     return m_device;

src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsintegration.h

@@ -69,6 +69,7 @@ public:
     bool hasCapability(QPlatformIntegration::Capability cap) const override;
     void waitForVSync(QPlatformSurface *surface) const override;
     bool supportsPBuffers() const override;
+    void *nativeResourceForIntegration(const QByteArray &name) override;
 
     QKmsDevice *device() const;
     QKmsScreenConfig *screenConfig() const;