Adding Qt stack to embedded linux kerenel

[embdev]

for testing purposes, is it possible to install the qt-everywhere-opensource-src-4.8.6 on the host computer, and then run the qt demos on my embedded Linux (target board) via NFS to retrieve the bin files from my host computer?

I tried this method but I get the following error:

[Qojote]

You really have to cross compile the Qt libraries for your target device. Therefore you need all the tools like *-g++.
Its quite useful for development when your whole rootfs is mounted via NFS.

[SGaist]

@Qojote The cross-compiling is correct. However, the cross-compiler doesn't come with the target rootfs. It's part of the host tools usually provided with the SDK.

[Qojote]

Correct. It was just a hint for the future.

[embdev]

ok, fyi, I've previously flashed in the vendor kernel image, rootfs and uboot. So right now i'll need to use the vendor's CC to make / compile all the Qt files in Qt-everywhere-opensource package?

[SGaist]

Yes, usually, the SDK provides the cross-compiler or if not, a mean to get one. What you will also need is the "dev" version of the packages you installed on your rootfs in order to get the dependencies needed for Qt and your application (e.g. OpenSSL)

[embdev]

I managed to compiled executable files for my embedded Linux board using arms arch. using my SDK compiler (using the Qt-everywhere-opensource-4.8.6).

FYI, because i'm just want to run a quick test for the Qt demos, i'm actually accessing the following files below (i.e. framebuffer; deform; books) on my Putty terminal, via my NSF that is linked to the host computer running on Ubuntu.

In addition, my lib folder in my embedded development board does nt contain the Qt lib files, but those Qt lib files are instead residing in my NSF folder. Do I also need to append my .profile file in my embedded Linux to point to the NSF path for the required lib files?

Will these pose problems as described in the following 3 errors when i'm executing the demos / examples in my putty terminal (i.e. running on embedded development board)?

Error 1:
When I tried to execute a Qt demo in my Putty terminal, it says:
/mnt/QtEmbedded-4.8.6-arm/examples/qws/framebuffer # ./framebuffer
Error: cannot open framebuffer device: Operation not permitted

Error 2:
when I tried to execute deform demo on putty terminal, it says:
/mnt/QtEmbedded-4.8.6-arm/demos/deform # ./deform Bus error

Error 3:
when I tried to execute books demo on putty terminal, it says:
./books: error while loading shared libraries: libQtSql.so.4: cannot open shared object file: No such file or directory

[SGaist]

1. You're a standard user and the /dev/fb0 access rights don't include you

2. I don't remember exactly but IIRC, there was a device involved e.g. error accessing the frame buffer but not related to rights.

3. It usually means that you don't have the Qt libraries installed on your target.

[embdev]

Hi SGaist,
thanks for the note; which means I won't be able to run the Qt demos (that are residing on my HOST Ubuntu PC) on my target embedded board without the Qt lib?. I tried to point the path to the NFS in .profile file i.e.
PATH=/mnt/QtEmbedded-4.8.6-arm/bin
PATH=/mnt/QtEmbedded-4.8.6-arm/lib

but apparently this didn't help as I still can't run the demos.

For Point #1, is there a way to include access in fb0? apparently my kernel image doesn't support sudo function though, Does it mean I need to get a new kernel image with sudo function?

[SGaist]

If you don't have sudo you may have su alone.

Well, you're building an application with Qt, so unless you make everything static, then yes, you need Qt on your target.

Where are you setting PATH ?

[embdev]

I see. That probably explains why I can run the demos / examples on the host PC with the environment setup as my target board doesn't include Qt libraries. I'm setting my PATH in /etc/profile/ :

---

/etc/profile: system-wide .profile file for the Bourne shells

set_path_before()
{
[ -d $1 ] && PATH="$1:$PATH"
}

PATH="/usr/bin:/usr/sbin:/bin:/sbin"
set_path_before /usr/local/sbin
set_path_before /usr/local/bin

*************************************************

PATH to Qt lib & bin on HOST PC

------------------------------

PATH=/mnt/QtEmbedded-4.8.6-arm/bin:$PATH
PATH=/mnt/QtEmbedded-4.8.6-arm/lib:$PATH

************************************************

LD_LIBRARY_PATH="/usr/local/lib:/usr/lib"

export PATH

---

How about if I copy the entire Qt lib from HOST to TARGET, and then point the path to my TARGET/lib files, would that work if I run the Qt demo on the HOST (via NFS), the Qt lib now sitting on my TARGET board?

[embdev]

btw, I tried to make directory Qtlib and then copy the entire Qt lib from my HOST PC into my TARGET BOARD (/Qtlib):

mkdir /lib/Qtlib
cp -r /mnt/QtEmbedded-4.8.6-arm/lib /lib/Qtlib

However, when I tried to change my PATH on my TARGET BOARD, i'm unable to save the file in vi editor.
(i.e. /etc/profile)

At this juncture, I tried to create a mkdir 'test' on root to test out i.e. mkdir /home/test and was returned with the following error:

/ # mkdir /home/aa
mkdir: can't create directory '/home/aa': Cannot allocate memory

I tried to reboot embedded Linux but still unable to edit and save changes in my profile using vi editor.

My memory at that juncture is
Total = 119MB
Used = 35 MB
Free = 83 MB

[jsulm]

For /etc/profile you need root access. So first call su and then start vi.

[SGaist]

Linux is not Windows, PATH is only used to find executable not libraries.

You can use LD_LIBRARY_PATH for that.

[embdev]

@jsulm it seems that my su command is not functional; when I use the command, it'll just go from my root to /~. Nonetheless, when I execute vi, I don't need root access when I type [vi profile]

@SGaist Tkx, I've amended and appended LD_LIBRARY_PATH="/mnt/QtEmbedded-4.8.6-arm/lib" to my profile file in /etc/profile but i'm still having the same problem when running framebuffer - unable to find libQtGui.so.4.

Could it be during cross-compilation, I could have missed out any variables when performing [Make] command?

[SGaist]

Were did you modify these variables ?

[embdev]

I didn't modify any source code variables though, I just did a ./configure, followed by make and make install that installs Qt-everywhere-opensource-4.8.6 into my /local/Trolltech folder

[embdev]

btw, i'm looking at qt-everywhere-enterprise-5.7 sources and what does it mean by 'sysroot'? Where may I locate my sysroot path?
http://doc.qt.io/qt-5/embedded-linux.html

[jsulm]

@embdev sysroot is the file-system (or part of it) of your target device. You can mount it wherever you want (or just copy it to a location). You need the sysroot to be able to cross-compile for your target as it contains all the libs and header files.

[embdev]

I compiled the qt-everywhere-enterprise-4.8.6 sources with static libraries and tried to run on my embedded Linux but have a new error:

QScreenLinuxFb::connect:No such file or directory.
Error opening framebuffer device /dev/fb0

There's a framebuffer stack on my embedded Linux that came with the vendor's SDK, which i'd need to run in the background

i.e. ./hifb &

However once I returned to command prompt and tried running Qt demo e.g. ./deform -qws, I've the errors as mentioned above .

Do you've any advice on how to bypass / resolve this error so I can at least display Qt demo on my embedded board?