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I've built Qt (with cross-compiler) from Ubuntu VM to Raspbian (Raspberry pi model 3 B+), so it can deploy apps via ssh.

Qt config:

Building on: linux-g++ (x86_64, CPU features: mmx sse sse2)
Building for: devices/linux-rasp-pi3-vc4-g++ (arm, CPU features: neon)
Target compiler: gcc 7.5.0
Configuration: cross_compile compile_examples enable_new_dtags largefile neon precompile_header shared shared rpath release c++11 c++14 c++1z concurrent dbus reduce_exports stl
Build options:
  Mode ................................... release
  Optimize release build for size ........ no
  Building shared libraries .............. yes
  Using C standard ....................... C11
  Using C++ standard ..................... C++17
  Using ccache ........................... no
  Using new DTAGS ........................ yes
  Relocatable ............................ yes
  Using precompiled headers .............. yes
  Using LTCG ............................. no
  Target compiler supports:
    NEON ................................. yes
  Build parts ............................ libs
Qt modules and options:
  Qt Concurrent .......................... yes
  Qt D-Bus ............................... yes
  Qt D-Bus directly linked to libdbus .... yes
  Qt Gui ................................. yes
  Qt Network ............................. yes
  Qt Sql ................................. yes
  Qt Testlib ............................. yes
  Qt Widgets ............................. yes
  Qt Xml ................................. yes
Support enabled for:
  Using pkg-config ....................... yes
  udev ................................... yes
  Using system zlib ...................... yes
  Zstandard support ...................... no
Qt Core:
  DoubleConversion ....................... yes
    Using system DoubleConversion ........ yes
  GLib ................................... yes
  iconv .................................. no
  ICU .................................... yes
  Built-in copy of the MIME database ..... yes
  Tracing backend ........................ <none>
  Logging backends:
    journald ............................. no
    syslog ............................... no
    slog2 ................................ no
  PCRE2 .................................. yes
    Using system PCRE2 ................... yes
Qt Network:
  getifaddrs() ........................... yes
  IPv6 ifname ............................ yes
  libproxy ............................... no
  Linux AF_NETLINK ....................... yes
  OpenSSL ................................ yes
    Qt directly linked to OpenSSL ........ no
  OpenSSL 1.1 ............................ yes
  DTLS ................................... yes
  OCSP-stapling .......................... yes
  SCTP ................................... no
  Use system proxies ..................... yes
  GSSAPI ................................. no
Qt Gui:
  Accessibility .......................... yes
  FreeType ............................... yes
    Using system FreeType ................ yes
  HarfBuzz ............................... yes
    Using system HarfBuzz ................ yes
  Fontconfig ............................. yes
  Image formats:
    GIF .................................. yes
    ICO .................................. yes
    JPEG ................................. yes
      Using system libjpeg ............... yes
    PNG .................................. yes
      Using system libpng ................ yes
  Text formats:
    HtmlParser ........................... yes
    CssParser ............................ yes
    OdfWriter ............................ yes
    MarkdownReader ....................... yes
      Using system libmd4c ............... no
    MarkdownWriter ....................... yes
  EGL .................................... yes
  OpenVG ................................. no
  OpenGL:
    Desktop OpenGL ....................... no
    OpenGL ES 2.0 ........................ yes
    OpenGL ES 3.0 ........................ yes
    OpenGL ES 3.1 ........................ yes
    OpenGL ES 3.2 ........................ yes
  Vulkan ................................. yes
  Session Management ..................... yes
Features used by QPA backends:
  evdev .................................. yes
  libinput ............................... yes
  INTEGRITY HID .......................... no
  mtdev .................................. yes
  tslib .................................. yes
  xkbcommon .............................. yes
  X11 specific:
    XLib ................................. yes
    XCB Xlib ............................. yes
    EGL on X11 ........................... yes
QPA backends:
  DirectFB ............................... no
  EGLFS .................................. yes
  EGLFS details:
    EGLFS OpenWFD ........................ no
    EGLFS i.Mx6 .......................... no
    EGLFS i.Mx6 Wayland .................. no
    EGLFS RCAR ........................... no
    EGLFS EGLDevice ...................... yes
    EGLFS GBM ............................ yes
    EGLFS VSP2 ........................... no
    EGLFS Mali ........................... no
    EGLFS Raspberry Pi ................... no
    EGLFS X11 ............................ yes
  LinuxFB ................................ yes
  VNC .................................... yes
  XCB:
    Using system-provided XCB libraries .. yes
    XCB XKB .............................. yes
    XCB XInput ........................... yes
    Native painting (experimental) ....... no
    GL integrations:
      GLX Plugin ......................... no
      EGL-X11 Plugin ..................... yes
Qt Sql:
  SQL item models ........................ yes
Qt Widgets:
  GTK+ ................................... no
  Styles ................................. Fusion Windows
Qt PrintSupport:
  CUPS ................................... no
Qt Sql Drivers:
  DB2 (IBM) .............................. no
  InterBase .............................. no
  MySql .................................. no
  OCI (Oracle) ........................... no
  ODBC ................................... no
  PostgreSQL ............................. yes
  SQLite2 ................................ yes
  SQLite ................................. yes
    Using system provided SQLite ......... no
  TDS (Sybase) ........................... yes
Qt Testlib:
  Tester for item models ................. yes
Serial Port:
  ntddmodm ............................... no
Qt SerialBus:
  Socket CAN ............................. yes
  Socket CAN FD .......................... yes
  SerialPort Support ..................... yes
Further Image Formats:
  JasPer ................................. no
  MNG .................................... no
  TIFF ................................... yes
    Using system libtiff ................. no
  WEBP ................................... yes
    Using system libwebp ................. yes
Qt QML:
  QML network support .................... yes
  QML debugging and profiling support .... yes
  QML just-in-time compiler .............. yes
  QML sequence object .................... yes
  QML XML http request ................... yes
  QML Locale ............................. yes
Qt QML Models:
  QML list model ......................... yes
  QML delegate model ..................... yes
Qt Quick:
  Direct3D 12 ............................ no
  AnimatedImage item ..................... yes
  Canvas item ............................ yes
  Support for Qt Quick Designer .......... yes
  Flipable item .......................... yes
  GridView item .......................... yes
  ListView item .......................... yes
  TableView item ......................... yes
  Path support ........................... yes
  PathView item .......................... yes
  Positioner items ....................... yes
  Repeater item .......................... yes
  ShaderEffect item ...................... yes
  Sprite item ............................ yes
QtQuick3D:
  Assimp ................................. yes
  System Assimp .......................... no
Qt Scxml:
  ECMAScript data model for QtScxml ...... yes
Qt Gamepad:
  SDL2 ................................... no
Qt 3D:
  Assimp ................................. yes
  System Assimp .......................... no
  Output Qt3D Job traces ................. no
  Output Qt3D GL traces .................. no
  Use SSE2 instructions .................. no
  Use AVX2 instructions .................. no
  Aspects:
    Render aspect ........................ yes
    Input aspect ......................... yes
    Logic aspect ......................... yes
    Animation aspect ..................... yes
    Extras aspect ........................ yes
Qt 3D Renderers:
  OpenGL Renderer ........................ yes
Qt 3D GeometryLoaders:
  Autodesk FBX ........................... no
Qt Bluetooth:
  BlueZ .................................. no
  BlueZ Low Energy ....................... no
  Linux Crypto API ....................... no
  Native Win32 Bluetooth ................. no
  WinRT Bluetooth API (desktop & UWP) .... no
  WinRT advanced bluetooth low energy API (desktop & UWP) . no
Qt Sensors:
  sensorfw ............................... no
Qt Quick Controls 2:
  Styles ................................. Default Fusion Imagine Material Universal
Qt Quick Templates 2:
  Hover support .......................... yes
  Multi-touch support .................... yes
Qt Positioning:
  Gypsy GPS Daemon ....................... no
  WinRT Geolocation API .................. no
Qt Location:
  Qt.labs.location experimental QML plugin . yes
  Geoservice plugins:
    OpenStreetMap ........................ yes
    HERE ................................. yes
    Esri ................................. yes
    Mapbox ............................... yes
    MapboxGL ............................. yes
    Itemsoverlay ......................... yes
QtXmlPatterns:
  XML schema support ..................... yes
Qt Multimedia:
  ALSA ................................... yes
  GStreamer 1.0 .......................... yes
  GStreamer 0.10 ......................... no
  Video for Linux ........................ yes
  OpenAL ................................. no
  PulseAudio ............................. yes
  Resource Policy (libresourceqt5) ....... no
  Windows Audio Services ................. no
  DirectShow ............................. no
  Windows Media Foundation ............... no
Qt TextToSpeech:
  Flite .................................. no
  Flite with ALSA ........................ no
  Speech Dispatcher ...................... no
Qt Tools:
  QDoc ................................... no
Qt WebEngine Build Tools:
  Use System Ninja ....................... no
  Use System Gn .......................... no
  Jumbo Build Merge Limit ................ 8
  Developer build ........................ no
  QtWebEngine required system libraries:
    fontconfig ........................... yes
    dbus ................................. yes
    nss .................................. yes
    khr .................................. yes
    glibc ................................ yes
  QtWebEngine required system libraries for qpa-xcb:
    x11 .................................. no
    libdrm ............................... yes
    xcomposite ........................... no
    xcursor .............................. no
    xi ................................... no
    xtst ................................. no
  Optional system libraries used:
    re2 .................................. yes
    icu .................................. no
    libwebp, libwebpmux and libwebpdemux . yes
    opus ................................. yes
    ffmpeg ............................... no
    libvpx ............................... no
    snappy ............................... yes
    glib ................................. yes
    zlib ................................. yes
    minizip .............................. yes
    libevent ............................. yes
    jsoncpp .............................. yes
    protobuf ............................. no
    libxml2 and libxslt .................. yes
    lcms2 ................................ yes
    png .................................. yes
    JPEG ................................. yes
    harfbuzz ............................. yes
    freetype ............................. yes

I can build the project and get executable app file (if I copy it into Raspberry - it will work):

ELF 32-bit LSB executable, ARM, EABI5 version 1 (GNU/Linux), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 3.2.0, BuildID[sha1]=ac6935ff94eece0310f25438693924ca374e77e3, with debug_info, not stripped

But, when I try to run it remotely, like ./test_app, or deploy it using Qt creator's ssh connection, I got an Error on my Raspberry: Could not find DRM device! Aborted

So I have two questions:

  1. Why does my app works if I run it manually (I've tried to build/run different apps with different libs used) and doesn't work when I run it through ssh?
  2. What is the reason? I've read a lot of articles, but still don't get what does it have to do with "DRM device" (DRM - digital rights management, if I get it right)

There are a lot of questions (since 2017) about my problem, but none of them solved till now.

Cataract
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1 Answers1

2

DRM stands for "Direct Rendering Manager". https://fr.wikipedia.org/wiki/Direct_Rendering_Manager

In your Qt configuration, look at "QPA backends". It seems to support X11 and EGLFS, for example.

I don't know the exact difference between "if I run it manually" and "if I run it through ssh" but I guess environments are different. Maybe QT_QPA_PLATFORM and/or DISPLAY (for X11). Look at platform plugins for Qt: https://doc.qt.io/qt-5/embedded-linux.html

Richard Buchmann
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