yesterday I successfully build mtdev2tuio, but there were still some warnings left. So today I try to resolve these warnings. There are 4 warning of 3 types.
the first one is "Attempt to use kernel headers from user space" check the website
The problem comes from using wrong header files. To solve this problem, we should make our gcc to use correct include path. In our bsp, go to root of kernel and type the command sudo make headers_install ARCH=arm INSTALL_HDR_PATH=./usr/
It will generate header files of the kernel
check the usr directory and we find the include directory in it, good.
next, in our make file, we have to add this path for gcc while compiling arm-none-linux-gnueabi-gcc -nostdlib -I/media/DM8134/src/board-support/linux-2.6.37-psp04.04.00.01/usr/include/ -I/mnt/hgfs/share/qtuio/liblo/include/ -I/mnt/hgfs/share/qtuio/mtdev-1.1.2/include -c mtdev2tuio.c check the result, the warning disappeared, great!!
Next, let's take a look of these two warnings e-linux-gnueabi-ld: warning: library search path "/usr/local/lib/liblo/lib/" is unsafe for cross-compilation arm-none-linux-gnueabi-ld: warning: library search path "/usr/local/lib/mtdev/lib/" is unsafe for cross-compilation These warnings come with (probably) wrong lib path setting. We cross compile object files for TI DM8134 (ARM arch) but out library refer to the path of Ubuntu(i386). It seems something wrong. While I started to port TUIO to DM8134, I found a great reference. The author told us to cross compile necessary libs (liblo, mtdev), install them to /usr/local/lib/, and then load them in the linking stage. It is not wrong, but it is very dirty. The better way to solve these two warnings is to set the install path of libs to our development directory. In this case, it is under targetfs/usr/lib/. So first, install them to targetfs/usr/lib/.
Second, add the path to our ld command arm-none-linux-gnueabi-ld mtdev2tuio.o -o mtdev2tuio -L/media/DM8134/targetfs/usr/lib/liblo/lib/ -L/media/DM8134/targetfs/usr/lib/mtdev/lib/ -lmtdev -llo -lc -lgcc_s -lm check the result again
the warning disappeared Wwwonderful!! Last, the warning warning: cannot find entry symbol _start; defaulting to 000096e0 please refer to this website add "--entry main" to tell ld what the entry function is arm-none-linux-gnueabi-ld --entry main mtdev2tuio.o -o mtdev2tuio -L/media/DM8134/targetfs/usr/lib/liblo/lib/ -L/media/DM8134/targetfs/usr/lib/mtdev/lib/ -lmtdev -llo -lc -lgcc_s -lm
OK, we can see all warnings generated from gcc and ld are cleared. P.S. there is still a warning, this is because I use VM to develop, and it seems cause the clock skew.
refer to this article Building mtdev2tuio needs header files of mtdev and liblo, since these two packages are built and install into directories respectively. We can add -I option to gcc command arm-none-linux-gnueabi-gcc -I/mnt/hgfs/share/qtuio/liblo/include/ -I/mnt/hgfs/share/qtuio/mtdev-1.1.2/include -c mtdev2tuio.c
and we can find the object file is generated (mtdev2tuio.o).
next, link corresponding libs to generate executable. mtdev and liblo was made and installed into its directories, so we can use -L to load the path and -l to load the lib arm-none-linux-gnueabi-ld -o mtdev2tuio mtdev2tuio.o -L/media/DM8134/targetfs/lib -L/usr/lib/liblo/lib/ -L/usr/local/lib/mtdev/lib/ -lmtdev -llo and we get
God damn it! I never got so many errors in one make. No worry. It seems that we lack of some libs (printf, free) so add -lc to add libc into the link stage arm-none-linux-gnueabi-ld -o mtdev2tuio mtdev2tuio.o -L/media/DM8134/targetfs/lib -L/usr/lib/liblo/lib/ -L/usr/local/lib/mtdev/lib/ -lmtdev -llo -lc
again, we get a bunch of error messages. no worry. Just search Google and it give us a good result as usual the error message is about lacking libs of gcc, so find something looks like "libgcc" in our building environment
and we found there is a libgcc_s in lib, that is it. add it into our link command arm-none-linux-gnueabi-ld -o mtdev2tuio mtdev2tuio.o -L/media/DM8134/targetfs/lib -L/usr/lib/liblo/lib/ -L/usr/local/lib/mtdev/lib/ -lmtdev -llo -lc -lgcc_s press enter! unfortunately there are still errors while linking.
Search Google and I found it add -lm to the command arm-none-linux-gnueabi-ld -o mtdev2tuio mtdev2tuio.o -L/media/DM8134/targetfs/lib -L/usr/lib/liblo/lib/ -L/usr/local/lib/mtdev/lib/ -lmtdev -llo -lc -lgcc_s -lm
and we can find the binary is generated
There are still 3 warnings while linking. Leave it tomorrow. :Q
'const struct input_absinfo' has no member named 'resolution'
so check the include file first go to the include directory, and type the command : $CC -M mtdev.h to get the path of all header files the result is as follows
we can find that the file input.h is from CodeSourcery directory. We want to reference it from our source tree(/media/DM8134/src/...). So I set the env parameter export C_INCLUDE_PATH=/media/DM8134/src/board-support/linux-2.6.37-psp04.04.00.01/include observe the parameter
C_INCLUDE_PATH is now set make again
OK, we got a new error message. error: asm/bitsperlong.h: No such file or directory check my include path again, I find there is a "asm-generic" directory in it but no "asm" directory. brute force!! copy asm-generic to asm
OK make again
so it seems that it can be built now go to upper (mtdev) directory, make and install make lot of warnings...
make install remember to set PATH parameter when using sudo to make install sudo env PATH=$PATH make install
all files are installed into corresponding directories under /usr/local/lib/mtdev/
