Buildroot & QEMU notes

buildroot.rst

Buildroot & QEMU

Navigating menuconfig

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Building Commands

make xapp_dwm-rebuild

make BR2_JLEVEL=$(nproc)

Generic changes on default

• Change BR2_TOOLCHAIN_BUILDROOT to glibc (required by matplotlib)
• No need for BR2_TOOLCHAIN_BUILDROOT_WCHAR as it's uClibc thing
• Enable C++ required by many packages at BR2_TOOLCHAIN_BUILDROOT_CXX
• Enable BR2_CCACHE for quicker build
• Increase BR2_TARGET_ROOTFS_EXT2_SIZE size to 128M (quickly required)

Enabling X-server

• Enable BR2_PACKAGE_XORG7
• Enable BR2_PACKAGE_XSERVER_XORG_SERVER (modular)
• Enable "Dynamic using devtmpfs + eudev" for "/dev management" under System configuration.
• Enable drivers
  • BR2_PACKAGE_XDRIVER_XF86_INPUT_KEYBOARD
  • BR2_PACKAGE_XDRIVER_XF86_INPUT_MOUSE
  • BR2_PACKAGE_XDRIVER_XF86_VIDEO_CIRRUS (QEMU simulates this)
  • BR2_PACKAGE_XDRIVER_XF86_VIDEO_FBDEV
  • BR2_PACKAGE_XDRIVER_XF86_VIDEO_VESA
  • BR2_PACKAGE_XDRIVER_XF86_INPUT_EVDEV (QEMU tablet mode mouse)

Python Matplotlib

• Enable BR2_PACKAGE_PYTHON3
• Enable BR2_PACKAGE_PYTHON_MATPLOTLIB

Buildroot has matplotlib-qt if you have qt5 enabled - Enable QT5 - Enable mesa3d backend (qt supports OpenGL ES also)

Fixing mouse

By default it seems the mouse doesn't want to move

I was able to fix this by manual xorg.conf. This can be done with following steps:

1. Launch qemu with "-usb -device usb-tablet"
2. Find /dev/eventX for "QEMU QEMU USB Tablet" with "cat /proc/bus/input/devices"
3. Stop Xorg with "/etc/init.d/S40xorg stop"
4. Create default Xorg configuration with "Xorg -configure"
5. Modify the "InputDevice" for mouse to:

Section "InputDevice"
        Identifier  "Mouse0"
        Driver      "evdev"
        Option      "Device" "/dev/input/event2"
EndSection

Modifying rootfs files

1. Create "rootfs_overlay" folder to project root.
2. Set BR2_ROOTFS_OVERLAY to "rootfs_overlay"