1 files changed, 59 insertions, 5 deletions

diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldevicescreen.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldevicescreen.cpp
index eadb079f70..3fc46cd224 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldevicescreen.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldevicescreen.cpp
@@ -13,12 +13,63 @@ Q_DECLARE_LOGGING_CATEGORY(qLcEglfsKmsDebug)
 
 QEglFSKmsEglDeviceScreen::QEglFSKmsEglDeviceScreen(QEglFSKmsDevice *device, const QKmsOutput &output)
     : QEglFSKmsScreen(device, output)
+    , m_default_fb_handle(uint32_t(-1))
+    , m_default_fb_id(uint32_t(-1))
 {
+    const int fd = device->fd();
+
+    struct drm_mode_create_dumb createRequest;
+    createRequest.width = output.size.width();
+    createRequest.height = output.size.height();
+    createRequest.bpp = 32;
+    createRequest.flags = 0;
+
+    qCDebug(qLcEglfsKmsDebug, "Creating dumb fb %dx%d", createRequest.width, createRequest.height);
+
+    int ret = drmIoctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &createRequest);
+    if (ret < 0)
+        qFatal("Unable to create dumb buffer.\n");
+
+    m_default_fb_handle = createRequest.handle;
+
+    uint32_t handles[4] = { 0, 0, 0, 0 };
+    uint32_t pitches[4] = { 0, 0, 0, 0 };
+    uint32_t offsets[4] = { 0, 0, 0, 0 };
+
+    handles[0] = createRequest.handle;
+    pitches[0] = createRequest.pitch;
+    offsets[0] = 0;
+
+    ret = drmModeAddFB2(fd, createRequest.width, createRequest.height, DRM_FORMAT_ARGB8888, handles,
+                        pitches, offsets, &m_default_fb_id, 0);
+    if (ret)
+        qFatal("Unable to add fb\n");
+
+    qCDebug(qLcEglfsKmsDebug, "Added dumb fb %dx%d handle:%u pitch:%d id:%u", createRequest.width, createRequest.height,
+        createRequest.handle, createRequest.pitch, m_default_fb_id);
 }
 
 QEglFSKmsEglDeviceScreen::~QEglFSKmsEglDeviceScreen()
 {
-    const int remainingScreenCount = qGuiApp->screens().count();
+    int ret;
+    const int fd = device()->fd();
+
+    if (m_default_fb_id != uint32_t(-1)) {
+        ret = drmModeRmFB(fd, m_default_fb_id);
+        if (ret)
+            qErrnoWarning("drmModeRmFB failed");
+    }
+
+    if (m_default_fb_handle != uint32_t(-1)) {
+        struct drm_mode_destroy_dumb destroyRequest;
+        destroyRequest.handle = m_default_fb_handle;
+
+        ret = drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroyRequest);
+        if (ret)
+            qErrnoWarning("DRM_IOCTL_MODE_DESTROY_DUMB failed");
+    }
+
+    const int remainingScreenCount = qGuiApp->screens().size();
     qCDebug(qLcEglfsKmsDebug, "Screen dtor. Remaining screens: %d", remainingScreenCount);
     if (!remainingScreenCount && !device()->screenConfig()->separateScreens())
         static_cast<QEglFSKmsEglDevice *>(device())->destroyGlobalCursor();
@@ -53,8 +104,11 @@ void QEglFSKmsEglDeviceScreen::waitForFlip()
         if (alreadySet) {
             // Maybe detecting the DPMS mode could help here, but there are no properties
             // exposed on the connector apparently. So rely on an env var for now.
-            static bool alwaysDoSet = qEnvironmentVariableIntValue("QT_QPA_EGLFS_ALWAYS_SET_MODE");
-            if (!alwaysDoSet) {
+            // Note that typically, we need to set crtc with the default fb even if the
+            // mode did not change, unless QT_QPA_EGLFS_ALWAYS_SET_MODE is explicitly specified.
+            static bool envVarSet = false;
+            static bool alwaysDoSet = qEnvironmentVariableIntValue("QT_QPA_EGLFS_ALWAYS_SET_MODE", &envVarSet);
+            if (envVarSet && !alwaysDoSet) {
                 qCDebug(qLcEglfsKmsDebug, "Mode already set");
                 return;
             }
@@ -62,7 +116,7 @@ void QEglFSKmsEglDeviceScreen::waitForFlip()
 
         qCDebug(qLcEglfsKmsDebug, "Setting mode");
         int ret = drmModeSetCrtc(fd, op.crtc_id,
-                                 uint32_t(-1), 0, 0,
+                                 m_default_fb_id, 0, 0,
                                  &op.connector_id, 1,
                                  &op.modes[op.mode]);
         if (ret)
@@ -74,7 +128,7 @@ void QEglFSKmsEglDeviceScreen::waitForFlip()
 
         if (op.wants_forced_plane) {
             qCDebug(qLcEglfsKmsDebug, "Setting plane %u", op.forced_plane_id);
-            int ret = drmModeSetPlane(fd, op.forced_plane_id, op.crtc_id, uint32_t(-1), 0,
+            int ret = drmModeSetPlane(fd, op.forced_plane_id, op.crtc_id, m_default_fb_id, 0,
                                       0, 0, w, h,
                                       0 << 16, 0 << 16, op.size.width() << 16, op.size.height() << 16);
             if (ret == -1)