Add a tech preview eglfs device integration for VSP2 composition

This creates a new device integration for eglfs, eglfs_kms_vsp2, that's very
similar to eglfs_kms_gbm, but includes an extra step for doing VSP2 hardware
compositing.

The main Qt content is drawn to double buffered off-screen GBM buffers which
are converted using drmPrimeHandleToFD so we get DMA buffer file descriptors
that can be used by the VSP2 blending hardware. The blending hardware writes to
double buffered DRM dumb buffers, which are flipped with drmModePageFlip.

Communicating with the VSP2 is done using the Video4Linux2 (V4L2) streaming
API. There are two steps in creating abstractions for this. First, there is the
QLinuxMedia class that consists of a Qt style wrapper for V4L2 without anything
VSP2 specific. Second, there is QVsp2BlendingDevice which hides some of the
streaming details of the VSP2 and has some level of error recovery. Both
classes include a fair bit of logging and error reporting.

The patch is written with Wayland compositors in mind, but should work for
other use cases as well.

This is just the basic support to make compositing work, additional features
may be added in subsequent patches, i.e:

- Auto-detect VSP2 (-feature-vsp2 currently needs to be explicitly enabled).
- Support for setting the alpha value of a layer.
- Support clipping layers.
- Support for scaling layers.
- Support for other output formats than RGBA32.
- Hardware cursor support.
- Support foreign layers below the main Qt layer.
- Support for memory mapped and user pointer buffer types (currently only DMA
  buffers are supported).

Change-Id: I1917d2dbdbaeded0d9c021baaa799d56afe1a9bd
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 115 insertions, 0 deletions

diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_vsp2/qeglfskmsvsp2screen.h b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_vsp2/qeglfskmsvsp2screen.h
new file mode 100644
index 0000000000..19f65e7e7d
--- /dev/null
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_vsp2/qeglfskmsvsp2screen.h
@@ -0,0 +1,115 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Pier Luigi Fiorini <pierluigi.fiorini@gmail.com>
+** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2016 Pelagicore AG
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QEGLFSKMSVSP2SCREEN_H
+#define QEGLFSKMSVSP2SCREEN_H
+
+#include "qeglfskmsscreen.h"
+#include "qvsp2blendingdevice.h"
+#include <QtCore/QMutex>
+
+#include <gbm.h>
+
+QT_BEGIN_NAMESPACE
+
+class QEglFSKmsVsp2Screen : public QEglFSKmsScreen
+{
+public:
+    QEglFSKmsVsp2Screen(QKmsDevice *device, const QKmsOutput &output);
+
+    gbm_surface *createSurface();
+    void resetSurface();
+
+    void initDumbFrameBuffers();
+    void initVsp2();
+
+    //TODO: use a fixed index API instead of auto increment?
+    int addLayer(int dmabufFd, const QSize &size, const QPoint &position, uint drmPixelFormat, uint bytesPerLine);
+    void setLayerBuffer(int id, int dmabufFd);
+    void setLayerPosition(int id, const QPoint &position);
+    bool removeLayer(int id);
+    void addBlendListener(void (*callback)());
+
+    void flip();
+    void blendAndFlipDrm();
+
+private:
+    class Blender : public QObject // This is a workaround we really would want the screen to be a QObject
+    {
+    public:
+        Blender(QEglFSKmsVsp2Screen *screen) : m_screen(screen) {}
+        ~Blender() override {}
+        bool event(QEvent *event) override;
+        QEglFSKmsVsp2Screen *m_screen = nullptr;
+    };
+    QScopedArrayPointer<Blender> m_blender;
+
+    gbm_surface *m_gbmSurface = nullptr;
+    gbm_bo *m_currentGbmBo = nullptr;
+    gbm_bo *m_nextGbmBo = nullptr;
+
+    QScopedPointer<QVsp2BlendingDevice> m_blendDevice;
+
+    struct FrameBuffer { //these are for buffers that have been blended by the bru
+        uint32_t drmBufferId = 0;
+        int dmabufFd = -1;
+    };
+    std::array<FrameBuffer, 2> m_frameBuffers;
+    uint m_backFb = 0;
+    void initDumbFrameBuffer(FrameBuffer &fb);
+    QVector<void (*)()> m_blendFinishedCallbacks;
+
+    struct DmaBuffer { //these are for qt buffers before blending with additional layers (gbm buffer data)
+        int dmabufFd = -1;
+    };
+    static void dmaBufferDestroyedHandler(gbm_bo *gbmBo, void *data);
+    DmaBuffer *dmaBufferForGbmBuffer(gbm_bo *gbmBo);
+
+    void ensureModeSet();
+    void doDrmFlip();
+
+    bool m_blendScheduled = false;
+    int m_qtLayer = 0; //TODO: add API for changing this
+};
+
+QT_END_NAMESPACE
+
+#endif // QEGLFSKMSVSP2SCREEN_H