AM5708: Framebuffer rotation

Hi Sebastian,

There is an older thread that refers to the same topic. You should be able to refer to this thread to help get started with rotating the display. This is an older legacy device so a lot of current support is limited.

Thanks,
Sarabesh S.

Hello again,

We have found a workaround to our rotation problem, hope it helps others with similar issues.

1. To rotate the splash in U-Boot, we just use a rotated image ;-)
2. To rotate the "framebuffer console" or fbcon, we add to the kernel command line (in u-boot bootargs): fbcon=rotate:2 This also rotates the linux logo (splash)
3. The problem we were trying to solve with this thread was the QT application rotation, which runs in framebuffer. A first approach was to use the solutions in this StackOverflow answer. Although it worked, for some reason button press events were received several times, likely because of our application architecture, but if no rotation was applied it worked well. The solution was to patch QT 5 libraries, following this post and doing some rework since the patch provided there is for an older version of QT 5.

Since we are using Yocto, I had to add the patch in meta-qt5/recipes-qt/qt5/qtbase/0023-linuxfb_rotation.patch and modify meta-qt5/recipes-qt/qt5/qtbase/qtbase_git.bb to include it among the other patches.

The patch id modified so QT applications are rotated 180 degrees by default, but you can rotate to other values as explained in borkedlabs.com post, with 

export QT_QPA_PLATFORM=linuxfb:fb=/dev/fb0:rotation=90

This is the patch content:

diff --git a/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp b/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp
index a66c9fa..a5b5f13 100644
--- a/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp
+++ b/src/plugins/platforms/linuxfb/qlinuxfbscreen.cpp
@@ -287,7 +287,7 @@ static void blankScreen(int fd, bool on)
}
QLinuxFbScreen::QLinuxFbScreen(const QStringList &args)
- : mArgs(args), mFbFd(-1), mTtyFd(-1), mBlitter(0)
+ : mArgs(args), mFbFd(-1), mTtyFd(-1), mBlitter(0), mRotation(180)
{
mMmap.data = 0;
}
@@ -313,6 +313,7 @@ bool QLinuxFbScreen::initialize()
QRegularExpression mmSizeRx(QLatin1String("mmsize=(\\d+)x(\\d+)"));
QRegularExpression sizeRx(QLatin1String("size=(\\d+)x(\\d+)"));
QRegularExpression offsetRx(QLatin1String("offset=(\\d+)x(\\d+)"));
+ QRegularExpression rotationRx(QLatin1String("rotation=(0|90|180|270)"));
QString fbDevice, ttyDevice;
QSize userMmSize;
@@ -334,6 +335,8 @@ bool QLinuxFbScreen::initialize()
ttyDevice = match.captured(1);
else if (arg.contains(fbRx, &match))
fbDevice = match.captured(1);
+ else if (arg.contains(rotationRx, &match))
+ mRotation = match.captured(1).toInt();
}
if (fbDevice.isEmpty()) {
@@ -372,10 +375,17 @@ bool QLinuxFbScreen::initialize()
mDepth = determineDepth(vinfo);
mBytesPerLine = finfo.line_length;
QRect geometry = determineGeometry(vinfo, userGeometry);
+ QRect originalGeometry = geometry;
+ if( mRotation == 90 || mRotation == 270 )
+ {
+ int tmp = geometry.width();
+ geometry.setWidth(geometry.height());
+ geometry.setHeight(tmp);
+ }
+
mGeometry = QRect(QPoint(0, 0), geometry.size());
mFormat = determineFormat(vinfo, mDepth);
- mPhysicalSize = determinePhysicalSize(vinfo, userMmSize, geometry.size());
-
+ mPhysicalSize = determinePhysicalSize(vinfo, userMmSize, originalGeometry.size());
// mmap the framebuffer
mMmap.size = finfo.smem_len;
uchar *data = (unsigned char *)mmap(0, mMmap.size, PROT_READ | PROT_WRITE, MAP_SHARED, mFbFd, 0);
@@ -384,11 +394,11 @@ bool QLinuxFbScreen::initialize()
return false;
}
- mMmap.offset = geometry.y() * mBytesPerLine + geometry.x() * mDepth / 8;
+ mMmap.offset = originalGeometry.y() * mBytesPerLine + originalGeometry.x() * mDepth / 8;
mMmap.data = data + mMmap.offset;
QFbScreen::initializeCompositor();
- mFbScreenImage = QImage(mMmap.data, geometry.width(), geometry.height(), mBytesPerLine, mFormat);
+ mFbScreenImage = QImage(mMmap.data, originalGeometry.width(), originalGeometry.height(), mBytesPerLine, mFormat);
mCursor = new QFbCursor(this);
@@ -414,8 +424,27 @@ QRegion QLinuxFbScreen::doRedraw()
mBlitter->setCompositionMode(QPainter::CompositionMode_Source);
for (const QRect &rect : touched)
+ {
+ if( mRotation == 90 || mRotation == 270 )
+ {
+ mBlitter->translate(mGeometry.height()/2, mGeometry.width()/2);
+ }
+ else if( mRotation == 180 )
+ {
+ mBlitter->translate(mGeometry.width()/2, mGeometry.height()/2);
+ }
+
+ if( mRotation != 0 )
+ {
+ mBlitter->rotate(mRotation);
+ mBlitter->translate(-mGeometry.width()/2, -mGeometry.height()/2);
+ }
+
mBlitter->drawImage(rect, mScreenImage, rect);
+ mBlitter->resetTransform();
+ }
+
return touched;
}
diff --git a/src/plugins/platforms/linuxfb/qlinuxfbscreen.h b/src/plugins/platforms/linuxfb/qlinuxfbscreen.h
index 1997d46..a34414f 100644
--- a/src/plugins/platforms/linuxfb/qlinuxfbscreen.h
+++ b/src/plugins/platforms/linuxfb/qlinuxfbscreen.h
@@ -57,6 +57,7 @@ private:
QStringList mArgs;
int mFbFd;
int mTtyFd;
+ int mRotation;
QImage mFbScreenImage;
int mBytesPerLine;