linuxfb/drm: Pick up the format from the config file

Like eglfs, linuxfb (when QT_QPA_FB_DRM=1) can be configured to
use a buffer and fb of a format other than the default XRGB8888.

Most notably, adding "mode": "rgb565" to the first output in the
config file pointed to by QT_QPA_KMS_CONFIG will switch over
to using 16 bpp dumb buffers and a QImage::Format_RGB16 wrapping
QImage. Note that linuxfb/drm has no multiple output support atm,
so only the first output is taken into account.

The BGR variants (e.g. xbgr8888) are available but cause no
difference when it comes to Qt's painting (still maps to RGB32 etc.).
This may need to be revisited later.

Has no effect on the regular (fbdev) path in linuxfb.

Task-number: QTBUG-63272
Change-Id: Ie7d0b05e3449b336104332d9568dab60b4bedaa8
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 66 insertions, 10 deletions

diff --git a/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp b/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp
index e15d6fee24..dcc1ef2790 100644
--- a/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp
+++ b/src/plugins/platforms/linuxfb/qlinuxfbdrmscreen.cpp
@@ -43,7 +43,6 @@
 // Multiscreen: QWindow-QScreen(-output) association. Needs some reorg (device cannot be owned by screen)
 // Find card via devicediscovery like in eglfs_kms.
 // Mode restore like QEglFSKmsInterruptHandler.
-// Formats other then 32 bpp?
 // grabWindow
 
 #include "qlinuxfbdrmscreen.h"
@@ -187,15 +186,67 @@ void QLinuxFbDevice::registerScreen(QPlatformScreen *screen,
     Q_UNREACHABLE();
 }
 
+static uint32_t bppForDrmFormat(uint32_t drmFormat)
+{
+    switch (drmFormat) {
+    case DRM_FORMAT_RGB565:
+    case DRM_FORMAT_BGR565:
+        return 16;
+    default:
+        return 32;
+    }
+}
+
+static int depthForDrmFormat(uint32_t drmFormat)
+{
+    switch (drmFormat) {
+    case DRM_FORMAT_RGB565:
+    case DRM_FORMAT_BGR565:
+        return 16;
+    case DRM_FORMAT_XRGB8888:
+    case DRM_FORMAT_XBGR8888:
+        return 24;
+    case DRM_FORMAT_XRGB2101010:
+    case DRM_FORMAT_XBGR2101010:
+        return 30;
+    default:
+        return 32;
+    }
+}
+
+static QImage::Format formatForDrmFormat(uint32_t drmFormat)
+{
+    switch (drmFormat) {
+    case DRM_FORMAT_XRGB8888:
+    case DRM_FORMAT_XBGR8888:
+        return QImage::Format_RGB32;
+    case DRM_FORMAT_ARGB8888:
+    case DRM_FORMAT_ABGR8888:
+        return QImage::Format_ARGB32;
+    case DRM_FORMAT_RGB565:
+    case DRM_FORMAT_BGR565:
+        return QImage::Format_RGB16;
+    case DRM_FORMAT_XRGB2101010:
+    case DRM_FORMAT_XBGR2101010:
+        return QImage::Format_RGB30;
+    case DRM_FORMAT_ARGB2101010:
+    case DRM_FORMAT_ABGR2101010:
+        return QImage::Format_A2RGB30_Premultiplied;
+    default:
+        return QImage::Format_ARGB32;
+    }
+}
+
 bool QLinuxFbDevice::createFramebuffer(QLinuxFbDevice::Output *output, int bufferIdx)
 {
     const QSize size = output->currentRes();
     const uint32_t w = size.width();
     const uint32_t h = size.height();
+    const uint32_t bpp = bppForDrmFormat(output->kmsOutput.drm_format);
     drm_mode_create_dumb creq = {
         h,
         w,
-        32,
+        bpp,
         0, 0, 0, 0
     };
     if (drmIoctl(fd(), DRM_IOCTL_MODE_CREATE_DUMB, &creq) == -1) {
@@ -207,10 +258,15 @@ bool QLinuxFbDevice::createFramebuffer(QLinuxFbDevice::Output *output, int buffe
     fb.handle = creq.handle;
     fb.pitch = creq.pitch;
     fb.size = creq.size;
-    qCDebug(qLcFbDrm, "Got a dumb buffer for size %dx%d, handle %u, pitch %u, size %u",
-            w, h, fb.handle, fb.pitch, (uint) fb.size);
+    qCDebug(qLcFbDrm, "Got a dumb buffer for size %dx%d and bpp %u: handle %u, pitch %u, size %u",
+            w, h, bpp, fb.handle, fb.pitch, (uint) fb.size);
+
+    uint32_t handles[4] = { fb.handle };
+    uint32_t strides[4] = { fb.pitch };
+    uint32_t offsets[4] = { 0 };
 
-    if (drmModeAddFB(fd(), w, h, 24, 32, fb.pitch, fb.handle, &fb.fb) == -1) {
+    if (drmModeAddFB2(fd(), w, h, output->kmsOutput.drm_format,
+                      handles, strides, offsets, &fb.fb, 0) == -1) {
         qErrnoWarning(errno, "Failed to add FB");
         return false;
     }
@@ -229,10 +285,10 @@ bool QLinuxFbDevice::createFramebuffer(QLinuxFbDevice::Output *output, int buffe
         return false;
     }
 
-    qCDebug(qLcFbDrm, "FB is %u, mapped at %p", fb.fb, fb.p);
+    qCDebug(qLcFbDrm, "FB is %u (DRM format 0x%x), mapped at %p", fb.fb, output->kmsOutput.drm_format, fb.p);
     memset(fb.p, 0, fb.size);
 
-    fb.wrapper = QImage(static_cast<uchar *>(fb.p), w, h, fb.pitch, QImage::Format_ARGB32);
+    fb.wrapper = QImage(static_cast<uchar *>(fb.p), w, h, fb.pitch, formatForDrmFormat(output->kmsOutput.drm_format));
 
     return true;
 }
@@ -357,10 +413,10 @@ bool QLinuxFbDrmScreen::initialize()
     QLinuxFbDevice::Output *output(m_device->output(0));
 
     mGeometry = QRect(QPoint(0, 0), output->currentRes());
-    mDepth = 32;
-    mFormat = QImage::Format_ARGB32;
+    mDepth = depthForDrmFormat(output->kmsOutput.drm_format);
+    mFormat = formatForDrmFormat(output->kmsOutput.drm_format);
     mPhysicalSize = output->kmsOutput.physical_size;
-    qCDebug(qLcFbDrm) << mGeometry << mPhysicalSize;
+    qCDebug(qLcFbDrm) << mGeometry << mPhysicalSize << mDepth << mFormat;
 
     QFbScreen::initializeCompositor();