docs: added more info to building.md

Signed-off-by: Mihai Tudor Panu <mihai.tudor.panu@intel.com>

docs/building.md

@@ -3,7 +3,15 @@ Building UPM                         {#building}
 
 UPM uses cmake in order to make compilation relatively painless. Cmake runs
 build out of tree so the recommended way is to clone from git and make a build/
-directory.
+directory. Failure to do an out-of-source build may cause issues when
+rebuilding later on.
+
+This project depends on libmraa, so that needs to be installed first. Use the
+following environment variables to configure the paths:
+
+    PKG_CONFIG_PATH=$PKG_CONFIG_PATH:.../mraa/build/lib/pkgconfig
+    CPLUS_INCLUDE_PATH=$CPLUS_INCLUDE_PATH:.../mraa/build/include
+    LIBRARY_PATH=$LIBRARY_PATH:.../mraa/build/lib
 
 UPM will attempt to build all directories inside src/ and they must contain
 individual CMakeLists.txt files.
@@ -19,27 +27,53 @@ Our cmake configure has a number of options, cmake-gui or ccmake can show you
 all the options. The interesting ones are detailed below:
 
 Changing install path from /usr/local to /usr
- -DCMAKE_INSTALL_PREFIX:PATH=/usr
+~~~~~~~~~~~~~
-
+-DCMAKE_INSTALL_PREFIX:PATH=/usr
+~~~~~~~~~~~~~
 Building debug build:
- -DCMAKE_BUILD_TYPE=DEBUG
+~~~~~~~~~~~~~
-
+-DCMAKE_BUILD_TYPE=DEBUG
+~~~~~~~~~~~~~
 Using clang instead of gcc:
- -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++
+~~~~~~~~~~~~~
-
+-DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++
+~~~~~~~~~~~~~
+Cross-compiling on a different system:
+~~~~~~~~~~~~~
+-DCMAKE_CXX_FLAGS:STRING=-m32 -march=i586
+-DCMAKE_C_FLAGS:STRING=-m32 -march=i586
+~~~~~~~~~~~~~
 Building with an older version of swig (swig 2.0+) requires the disabling of javascript:
- -DBUILDSWIGNODE=OFF
+~~~~~~~~~~~~~
-
+-DBUILDSWIGNODE=OFF
+~~~~~~~~~~~~~
 Disabling python module building
- -DBUILDSWIGPYTHON=OFF
+~~~~~~~~~~~~~
-
+-DBUILDSWIGPYTHON=OFF
+~~~~~~~~~~~~~
+Setting the python library to use:
+~~~~~~~~~~~~~
+-DPYTHON_LIBRARY:FILEPATH=/usr/lib/libpython2.7.so.1.0
+~~~~~~~~~~~~~
 Building doxygen doc
- -BUILDDOC=ON
+~~~~~~~~~~~~~
+-BUILDDOC=ON
+~~~~~~~~~~~~~
+You can also generate the include and lib directories containing all the sensor
+headers and library files respectively with *make install*. Further, you may
+choose to generate these only for a specific sensor you modified, and this can
+be achieved by building from the individual makefile of the sensor. Assuming
+you're in the build directory, to make the lcd module you would:
+
+~~~~~~~~~~~~~
+cd src/lcd
+make install
+~~~~~~~~~~~~~
 
 Often developers are only interested in building one module or even just the
 python/node module to do some quick testing using scripting. In order to do
 this you need to use the target name for the python or node module you want to
-rebuild. For example the lcd module target name is i2clcd. Therfore the python
+rebuild. For example the lcd module target name is i2clcd. Therefore the python
 module target name will be prefixed by _pyupm_. Just do the following to build
 only that module. Modules not using the UPM cmake macros may have different
 naming.
@@ -49,9 +83,9 @@ make _pyupm_i2clcd
 ~~~~~~~~~~~~~
 
 Sometimes you want to build a small C++ example against an installed library.
-This is fairly easy if installed systemwide. Just link against the correct
+This is fairly easy if installed system-wide. Just link against the correct
-librar (in this case libupm-tm1637) and then add /usr/include/upm to the loader
+library (in this case libupm-tm1637) and then add /usr/include/upm to the
-path:
+loader path:
 
 ~~~~~~~~~~~~
 g++ test.cxx -lupm_tm1637 -I/usr/include/upm