eglfs: allow forcing an overlay plane

Add a QT_QPA_EGLFS_KMS_PLANE_INDEX environment variable that applies
both to the GBM and EGLDevice backends. When set to a value between 0 and
the number of planes on the connector - 1, the chosen overlay plane will
be used for output, meaning there will be a drmModeSetPlane to configure,
and, in case of EGLDevice, the plane's corresponding EGL layer will get
chosen instead of the CRTC's.

Task-number: QTBUG-57386
Change-Id: I12c89472ea5730987052f39211fadc597d1302ef
Reviewed-by: Pasi Petäjäjärvi <pasi.petajajarvi@qt.io>

1 files changed, 27 insertions, 10 deletions

diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
index bed775ff81..d4df0dc66e 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmscreen.cpp
@@ -181,24 +181,41 @@ void QEglFSKmsGbmScreen::flip()
 
     FrameBuffer *fb = framebufferForBufferObject(m_gbm_bo_next);
 
-    if (!output().mode_set) {
-        int ret = drmModeSetCrtc(device()->fd(),
-                                 output().crtc_id,
+    QEglFSKmsOutput &op(output());
+    const int fd = device()->fd();
+    const uint32_t w = op.modes[op.mode].hdisplay;
+    const uint32_t h = op.modes[op.mode].vdisplay;
+
+    if (!op.mode_set) {
+        int ret = drmModeSetCrtc(fd,
+                                 op.crtc_id,
                                  fb->fb,
                                  0, 0,
-                                 &output().connector_id, 1,
-                                 &output().modes[output().mode]);
+                                 &op.connector_id, 1,
+                                 &op.modes[op.mode]);
 
-        if (ret) {
-            qErrnoWarning("Could not set DRM mode!");
+        if (ret == -1) {
+            qErrnoWarning(errno, "Could not set DRM mode!");
         } else {
-            output().mode_set = true;
+            op.mode_set = true;
             setPowerState(PowerStateOn);
+
+            if (!op.plane_set) {
+                op.plane_set = true;
+                if (op.wants_plane) {
+                    int ret = drmModeSetPlane(fd, op.plane_id, op.crtc_id,
+                                              uint32_t(-1), 0,
+                                              0, 0, w, h,
+                                              0 << 16, 0 << 16, w << 16, h << 16);
+                    if (ret == -1)
+                        qErrnoWarning(errno, "drmModeSetPlane failed");
+                }
+            }
         }
     }
 
-    int ret = drmModePageFlip(device()->fd(),
-                              output().crtc_id,
+    int ret = drmModePageFlip(fd,
+                              op.crtc_id,
                               fb->fb,
                               DRM_MODE_PAGE_FLIP_EVENT,
                               this);