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Embedded Linux

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Cross-compiling packages

./configure
make
make install

TFTP_ROOTFS=/tftpboot/rootfs
INSTALL_DIR=${TFTP_ROOTFS}/usr/local

# Make pkg-config use the target packages, not the hosts
export PKG_CONFIG_LIBDIR=${INSTALL_DIR}/lib/pkgconfig
export PKG_CONFIG_PATH=

./configure \
    --host=sh4-linux-gnu \
    --prefix=${INSTALL_DIR}

make
sudo make install

Common problems

• You don't have a configure script... Ok, maybe you have an autogen.sh script so run this first to generate a configure script. You don't have either scripts? Try autoreconf. Nothing? It's probably because the package doesn't use pkgconfig. In this case, you will have to look at the Makefile to see what you have to do to cross-compile it.

• When running sudo make install, the path to the toolchain is not setup for root. The simplest way is to pass the PATH environment variable to the call, e.g.

sudo env PATH=$PATH make install

• The package doesn't create pkgconfig files (e.g. zlib). This causes problems for any dependent package in that they won't be able to find the library. This is normally solved by adding the path to the header files to the CPPFLAGS env variable and adding the path to the library to the LDFLAGS linker env variable. For example, add these lines above the call to configure:
  

export CPPFLAGS="-I${INSTALL_DIR}/include"
export LDFLAGS="-L${INSTALL_DIR}/lib"

• The configure script doesn't support the --host= option (e.g. Framebuffer Viewer, fbv). Setting the CC env variable to the full name of the compiler usually gets round this. You will also have to specify any libraries used by the package, e.g.
  

make \
    CC=sh4-linux-gnu-gcc \
    LIBS="-lz -lpng -ljpeg"

• The package uses some build time path related variables at run-time (e.g. DirectFB). This means you cannot specify a prefix directory that is not in use on the final target, e.g. a tftpboot dir. So far, the only way we have found to build is to a local host directory (e.g. /usr/local/target) and then copy this output directory to the target file system under the same dir.

sudo make \
    DESTDIR=${A_LOCAL_DIR} install

• Qt Embedded for Linux 4.5.2 configure script examines the CC and CXX env variables. It is best to unset these and use the -platform and -xplatform options to set the host & target platforms respectively.

• Everything compiles ok, but fails to link. The main reason is because you have built on your host and pkgconfig has detected packages that were installed on your host and tried to use them. This is quite a common occurrence with GStreamer packages as they build a lot of different plugins that require other libraries to be installed. By default all plugins are enabled, and the configure script disables any for which it cannot find the required libraries. The simplest (and dirtiest) way to get round this is pass an option to ./configure to disable the troublesome feature.

• Everything built ok, but there is a missing library when you try to use it. The main reason is that you have installed into a directory that the system doesn't automatically look in for libraries. This can be fixed by setting the LD_LIBRARY_PATH env var on your target.

Qt 4.5.2 Touchscreen, mice & keyboards

The Linux kernel must bet set to create /dev/input/mouseX devices, so configure the kernel with:

CONFIG_INPUT_MOUSEDEV=y
CONFIG_INPUT_MOUSEDEV_PSAUX=y

When you have a touchscreen you will now get /dev/input/eventX and a corresponding /dev/input/mouseY. When you have a USB mouse plugged in you will get additional event & mouse entries in /dev/input. (Note: /dev/input/mice combines all mouseN events)

When configuring Qt you need to add these options:

-plugin-mouse-linuxis -qt-mouse-tslib

However Qt needs to be told to handle touchscreen and mice differently. You need to parse /proc/bus/input/devices to find out what you have attached. Since I'm using Busybox, I'm limited in the tools available to do the parsing. The Qt documentations says that multiple inputs are specified like this:

 export QWS_MOUSE_PROTO="<driver>[:<driver specific options>]
         <driver>[:<driver specific options>]
         <driver>[:<driver specific options>]"

The driver for touchscreen needs to be "tslib:/dev/input/eventX" whereas the USB mouse needs "IntelliMouse:/dev/input/ mouseY". If you list multiple inputs, just separate them with a space. Here's an simple awk script to set QWS_MOUSE_PROTO.

TMP=`grep -E 'Name|Handlers' /proc/bus/input/devices`

# Find the touchscreen if there
MOUSE=`echo $TMP | awk '
BEGIN{RS="N: Name="; FS="[NH]: ";}
    $2 ~ /mouse/ {
        ev = $2
        if ($1 ~ /Touchscreen/) {
            sub("Handlers=mouse[0-9]+ event", "", ev)
            text = sprintf("%s tslib:/dev/input/event%d",text,ev)
        }
        else {
            sub("Handlers=mouse", "", ev)
            text = sprintf("%s IntelliMouse:/dev/input/mouse%d",text,ev)
        }
    }
END{sub(" ", "", text); print text}
'`

export QWS_MOUSE_PROTO="$MOUSE"

Getting a USB keyboard working is easier, pass -qt-kbd-usb to configure and set QWS_KEYBOARD=Usb:/dev/input/eventX You can isolate the keyboard event inputs by adding this to the above script:

KEYBOARD=`echo $TMP | awk '
BEGIN{RS="N: Name="; FS="[NH]: ";}
    $2 ~ /kbd/ {
        ev = $2
        sub("Handlers=kbd event", "", ev)
        text = sprintf("%s Usb:/dev/input/event%d",text,ev)
    }
END{sub(" ", "", text); print text}
'`

export QWS_KEYBOARD="$KEYBOARD"

Normally I just pass the name of the Qt app to run to the scripts and run it within the script.



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Last modified Jan 2010