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>

2 files changed, 80 insertions, 0 deletions

diff --git a/src/platformheaders/eglfsfunctions/qeglfsfunctions.h b/src/platformheaders/eglfsfunctions/qeglfsfunctions.h
index b2f3b4c872..67522ec9be 100644
--- a/src/platformheaders/eglfsfunctions/qeglfsfunctions.h
+++ b/src/platformheaders/eglfsfunctions/qeglfsfunctions.h
@@ -57,6 +57,56 @@ public:
         if (func)
             func(filename);
     }
+
+    typedef int (*Vsp2AddLayerType)(const QScreen *screen, int dmabufFd, const QSize &size, const QPoint &position, uint drmPixelFormat, uint bytesPerLine);
+    static QByteArray vsp2AddLayerTypeIdentifier() { return QByteArrayLiteral("EglFSVsp2AddLayer"); }
+
+    //vsp2 functions are currently internal and preliminary (see qdoc file)
+    static int vsp2AddLayer(const QScreen *screen, int dmabufFd, const QSize &size, const QPoint &position, uint drmPixelFormat, uint bytesPerLine)
+    {
+        auto func = reinterpret_cast<Vsp2AddLayerType>(QGuiApplication::platformFunction(vsp2AddLayerTypeIdentifier()));
+        if (func)
+            return func(screen, dmabufFd, size, position, drmPixelFormat, bytesPerLine);
+        return 0;
+    }
+
+    typedef bool (*Vsp2RemoveLayerType)(const QScreen *screen, int id);
+    static QByteArray vsp2RemoveLayerTypeIdentifier() { return QByteArrayLiteral("EglFSVsp2RemoveLayer"); }
+
+    static bool vsp2RemoveLayer(const QScreen *screen, int id)
+    {
+        auto func = reinterpret_cast<Vsp2RemoveLayerType>(QGuiApplication::platformFunction(vsp2RemoveLayerTypeIdentifier()));
+        return func && func(screen, id);
+    }
+
+    typedef void (*Vsp2SetLayerBufferType)(const QScreen *screen, int id, int dmabufFd);
+    static QByteArray vsp2SetLayerBufferTypeIdentifier() { return QByteArrayLiteral("EglFSVsp2SetLayerBuffer"); }
+
+    static void vsp2SetLayerBuffer(const QScreen *screen, int id, int dmabufFd)
+    {
+        auto func = reinterpret_cast<Vsp2SetLayerBufferType>(QGuiApplication::platformFunction(vsp2SetLayerBufferTypeIdentifier()));
+        if (func)
+            func(screen, id, dmabufFd);
+    }
+
+    typedef bool (*Vsp2SetLayerPositionType)(const QScreen *screen, int id, const QPoint &position);
+    static QByteArray vsp2SetLayerPositionTypeIdentifier() { return QByteArrayLiteral("EglFSVsp2SetLayerPosition"); }
+
+    static bool vsp2SetLayerPosition(const QScreen *screen, int id, const QPoint &position)
+    {
+        auto func = reinterpret_cast<Vsp2SetLayerPositionType>(QGuiApplication::platformFunction(vsp2SetLayerPositionTypeIdentifier()));
+        return func && func(screen, id, position);
+    }
+
+    typedef void (*Vsp2AddBlendListenerType)(const QScreen *screen, void(*callback)());
+    static QByteArray vsp2AddBlendListenerTypeIdentifier() { return QByteArrayLiteral("EglFSVsp2AddBlendListener"); }
+
+    static void vsp2AddBlendListener(const QScreen *screen, void(*callback)())
+    {
+        auto func = reinterpret_cast<Vsp2AddBlendListenerType>(QGuiApplication::platformFunction(vsp2AddBlendListenerTypeIdentifier()));
+        if (func)
+            func(screen, callback);
+    }
 };
 
 
diff --git a/src/platformheaders/eglfsfunctions/qeglfsfunctions.qdoc b/src/platformheaders/eglfsfunctions/qeglfsfunctions.qdoc
index 6aca88e46e..d458d73155 100644
--- a/src/platformheaders/eglfsfunctions/qeglfsfunctions.qdoc
+++ b/src/platformheaders/eglfsfunctions/qeglfsfunctions.qdoc
@@ -65,3 +65,33 @@
     \c{QT_QPA_EGLFS_DISABLE_INPUT} is set or when building Qt without evdev
     support, this function will have no effect.
 */
+
+/*!
+    \fn int QEglFSFunctions::vsp2AddLayer(const QScreen *screen, int dmabufFd, const QSize &size, const QPoint &position, uint drmPixelFormat, uint bytesPerLine)
+    \internal
+    \preliminary
+*/
+
+/*!
+    \fn bool QEglFSFunctions::vsp2RemoveLayer(const QScreen *screen, int id)
+    \internal
+    \preliminary
+*/
+
+/*!
+    \fn void QEglFSFunctions::vsp2SetLayerBuffer(const QScreen *screen, int id, int dmabufFd)
+    \internal
+    \preliminary
+*/
+
+/*!
+    \fn bool QEglFSFunctions::vsp2SetLayerPosition(const QScreen *screen, int id, const QPoint &position)
+    \internal
+    \preliminary
+*/
+
+/*!
+    \fn void QEglFSFunctions::vsp2AddBlendListener(const QScreen *screen, void(*callback)())
+    \internal
+    \preliminary
+*/