EGLFS problem of Qt 5.7 on Raspberry

[ascnp]

Hi guys.
I now face a strange problem.
I just cross compile and build and install qt5.7 on raspberry pi3. Everything seems well, but when I want to use eglfs, it shows

This application failed to start because it could not find or load the Qt platform plugin "eglfs"
in "".

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, xcb.

Reinstalling the application may fix this problem.

but my platforms.so files are already install in the /usr/local/qt5pi-5.7/plugins/platforms, show as follow.

lxy@lxy:/usr/local/qt5pi-5.7/plugins/platforms$ ls
libqeglfs.a      libqlinuxfb.so      libqminimal.prl    libqxcb.a
libqeglfs.prl    libqminimal.a       libqminimal.so     libqxcb.prl
libqeglfs.so     libqminimalegl.a    libqoffscreen.a    libqxcb.so
libqlinuxfb.a    libqminimalegl.prl  libqoffscreen.prl
libqlinuxfb.prl  libqminimalegl.so   libqoffscreen.so

And I also run ldd libqeglfs.so and it shows as follow.

lxy@lxy:/usr/local/qt5pi-5.7/plugins/platforms$ ldd libqeglfs.so
	linux-vdso.so.1 =>  (0x7eedd000)
	/usr/lib/arm-linux-gnueabihf/libarmmem.so (0x76f6a000)
	libQt5EglDeviceIntegration.so.5 => /usr/local/qt5pi-5.7/plugins/platforms/./../../lib/libQt5EglDeviceIntegration.so.5 (0x76e9b000)
	libts-0.0.so.0 => /usr/local/tslib/lib/libts-0.0.so.0 (0x76e63000)
	libfontconfig.so.1 => /usr/lib/arm-linux-gnueabihf/libfontconfig.so.1 (0x76e26000)
	libfreetype.so.6 => /usr/lib/arm-linux-gnueabihf/libfreetype.so.6 (0x76daf000)
	libQt5DBus.so.5 => /usr/local/qt5pi-5.7/plugins/platforms/./../../lib/libQt5DBus.so.5 (0x76d37000)
	libXext.so.6 => /usr/lib/arm-linux-gnueabihf/libXext.so.6 (0x76d1b000)
	libX11.so.6 => /usr/lib/arm-linux-gnueabihf/libX11.so.6 (0x76c2a000)
	libdl.so.2 => /lib/arm-linux-gnueabihf/libdl.so.2 (0x76c17000)
	libgthread-2.0.so.0 => /usr/lib/arm-linux-gnueabihf/libgthread-2.0.so.0 (0x76c05000)
	libglib-2.0.so.0 => /lib/arm-linux-gnueabihf/libglib-2.0.so.0 (0x76b2d000)
	libEGL.so => /opt/vc/lib/libEGL.so (0x76af3000)
	libQt5Gui.so.5 => /usr/local/qt5pi-5.7/plugins/platforms/./../../lib/libQt5Gui.so.5 (0x766ad000)
	libQt5Core.so.5 => /usr/local/qt5pi-5.7/plugins/platforms/./../../lib/libQt5Core.so.5 (0x761fd000)
	libGLESv2.so => /opt/vc/lib/libGLESv2.so (0x761d8000)
	libpthread.so.0 => /lib/arm-linux-gnueabihf/libpthread.so.0 (0x761b4000)
	libstdc++.so.6 => /usr/lib/arm-linux-gnueabihf/libstdc++.so.6 (0x760a5000)
	libm.so.6 => /lib/arm-linux-gnueabihf/libm.so.6 (0x7602d000)
	libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0x76005000)
	libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0x75f19000)
	/lib/ld-linux-armhf.so.3 (0x54b7e000)
	libexpat.so.1 => /lib/arm-linux-gnueabihf/libexpat.so.1 (0x75ef1000)
	libz.so.1 => /lib/arm-linux-gnueabihf/libz.so.1 (0x75ece000)
	libpng12.so.0 => /lib/arm-linux-gnueabihf/libpng12.so.0 (0x75ea6000)
	libxcb.so.1 => /usr/lib/arm-linux-gnueabihf/libxcb.so.1 (0x75e82000)
	libpcre.so.3 => /lib/arm-linux-gnueabihf/libpcre.so.3 (0x75e25000)
	libbcm_host.so => /opt/vc/lib/libbcm_host.so (0x75dff000)
	libvchiq_arm.so => /opt/vc/lib/libvchiq_arm.so (0x75de8000)
	libvcos.so => /opt/vc/lib/libvcos.so (0x75dce000)
	librt.so.1 => /lib/arm-linux-gnueabihf/librt.so.1 (0x75db8000)
	libpcre16.so.3 => /usr/lib/arm-linux-gnueabihf/libpcre16.so.3 (0x75d62000)
	libXau.so.6 => /usr/lib/arm-linux-gnueabihf/libXau.so.6 (0x75d56000)
	libXdmcp.so.6 => /usr/lib/arm-linux-gnueabihf/libXdmcp.so.6 (0x75d42000)

All libs are linked but why it still cannot find eglfs? How to fix it?

[ascnp]

After I added QT_QPA_PLATFORM_PLUGIN_PATH, it shows as folllow.

This application failed to start because it could not find or load the Qt platform plugin "eglfs"
in "/usr/local/qt5pi-5.7/plugins/platforms".

Available platform plugins are: eglfs (from /usr/local/qt5pi-5.7/plugins/platforms), linuxfb (from /usr/local/qt5pi-5.7/plugins/platforms), minimal (from /usr/local/qt5pi-5.7/plugins/platforms), minimalegl (from /usr/local/qt5pi-5.7/plugins/platforms), offscreen (from /usr/local/qt5pi-5.7/plugins/platforms), xcb (from /usr/local/qt5pi-5.7/plugins/platforms), linuxfb, minimal, minimalegl, offscreen, xcb.

I'm really confused. Why the application failed to find eglfs, but qt says eglfs is available. And the eglfs is under the same path as I set.
I really need help!

[jsulm]

@ascnp It probably failed to load the plug-in. Is the plug-in built for the same architecture? Is the file maybe corrupted?
Set QT_DEBUG_PLUGINS variable before starting your application, maybe you will then see what happens (http://doc.qt.io/qt-5/debug.html).

[ascnp]

@jsulm I have rebuilt the qt5.7 and finally it can use, thanks for your help!

[qt_help]

@ascnp Could you please share the guide you followed to build the cross compilation environment for pi?