[Solved] Embedded Linux data directory
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Hi,
i've been trying to run Qt app on embedded device but i am getting following error:Cannot create Qt for Embedded Linux data directory: /tmp/qtembedded-0
This message is right because my root dir is read only partition, read write partition is mounted on /APPL. Is there any way to tell Qt to use ie /APPL/tmp to create data directory?
Thanks for you answers! -
Hmmm, good question and I'm not sure. A possible work around is to make /tmp writable. You could do this by making it a tmpfs filesystem type. ie add something like this to your /etc/fstab:
@
none /tmp/ tmpfs size=1M 0 0
@which would create a tmpfs ramdisk with maximum size of 1MB.
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OK I've done some digging and here's what I've found. The QWSServer object tries to create and listen on a local socket which by default is /tmp/qtembedded-0. This is done in qwindowsystem_qws.cpp:
@
void QWSServerPrivate::initServer(int flags)
{
Q_Q(QWSServer);
Q_ASSERT(!qwsServer);
qwsServer = q;
qwsServerPrivate = this;
disablePainting = false;
#ifndef QT_NO_QWS_MULTIPROCESS
ssocket = new QWSServerSocket(qws_qtePipeFilename(), q);
...
}
@where the function qws_qtePipeFilename() is defined in qapplication_qws.cpp and in turn calls qws_dataDir() which is in the same file. This in turn calls:
@
QString qws_dataDir()
{
static QString result;
if (!result.isEmpty())
return result;
result = QT_VFB_DATADIR(qws_display_id);
...
}
@where QT_VFB_DATADIR is a macro in qvfbhdr.h declared as:
@
#define QT_VFB_DATADIR(DISPLAY) QString("%1/qtembedded-%2-%3")
.arg(QT_QWS_TEMP_DIR).arg(getuid()).arg(DISPLAY)
@and finally we see trace down that we need QT_QWS_TEMP_DIR which is declared as:
@
#ifndef QT_QWS_TEMP_DIR
#define QT_QWS_TEMP_DIR "/tmp"
#endif
@So now we see that to locate the socket to a different location we somehow need to define QT_QWS_TEMP_DIR to a path of your choice that is writeable by the user your application will be running as.
I think you should be able to do this by defining QT_QWS_TEMP_DIR in the qplatformdefs.h of your custom mkspec. Then rebuild Qt Embedded for your target device and deploy and test.
Good luck!
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No problem. Either solution will work. It depends on your device configuration and other constraints as to what is the easiest. I've used the tmpfs approach too when we were booting a very minimal system using just an initramfs to launch only our application.