cpupower: Improve cpupower build process description

compilation and installation

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

make

su

make install

should suffice on most systems. It builds libcpupower to put in

/usr/lib; cpupower, cpufreq-bench_plot.sh to put in /usr/bin; and

cpufreq-bench to put in /usr/sbin. If you want to set up the paths

differently and/or want to configure the package to your specific

needs, you need to open "Makefile" with an editor of your choice and

edit the block marked CONFIGURATION.

There are 2 output directories - one for the build output and another for

the installation of the build results, that is the utility, library,

man pages, etc...

default directory

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

In the case of default directory, build and install process requires no

additional parameters:

build

-----

$ make

The output directory for the 'make' command is the current directory and

its subdirs in the kernel tree:

tools/power/cpupower

install

-------

$ sudo make install

'make install' command puts targets to default system dirs:

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

| Installing file        |               System dir                   |

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

| libcpupower            | /usr/lib                                   |

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

| cpupower               | /usr/bin                                   |

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

| cpufreq-bench_plot.sh  | /usr/bin                                   |

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

| man pages              | /usr/man                                   |

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

To put it in other words it makes build results available system-wide,

enabling any user to simply start using it without any additional steps

custom directory

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

There are 2 make's command-line variables 'O' and 'DESTDIR' that setup

appropriate dirs:

'O' - build directory

'DESTDIR' - installation directory. This variable could also be setup in

the 'CONFIGURATION' block of the "Makefile"

build

-----

$ make O=<your_custom_build_catalog>

Example:

$ make O=/home/hedin/prj/cpupower/build

install

-------

$ make O=<your_custom_build_catalog> DESTDIR=<your_custom_install_catalog>

Example:

$ make O=/home/hedin/prj/cpupower/build DESTDIR=/home/hedin/prj/cpupower \

> install

Notice that both variables 'O' and 'DESTDIR' have been provided. The reason

is that the build results are saved in the custom output dir defined by 'O'

variable. So, this dir is the source for the installation step. If only

'DESTDIR' were provided then the 'install' target would assume that the

build directory is the current one, build everything there and install

from the current dir.

The files will be installed to the following dirs:

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

| Installing file        |               System dir                   |

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

| libcpupower            | ${DESTDIR}/usr/lib                         |

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

| cpupower               | ${DESTDIR}/usr/bin                         |

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

| cpufreq-bench_plot.sh  | ${DESTDIR}/usr/bin                         |

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

| man pages              | ${DESTDIR}/usr/man                         |

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

If you look at the table for the default 'make' output dirs you will

notice that the only difference with the non-default case is the

${DESTDIR} prefix. So, the structure of the output dirs remains the same

regardles of the root output directory.

clean and uninstall

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

'clean' target is intended for cleanup the build catalog from build results

'uninstall' target is intended for removing installed files from the

installation directory

default directory

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

This case is a straightforward one:

$ make clean

$ make uninstall

custom directory

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

Use 'O' command line variable to remove previously built files from the

build dir:

$ make O=<your_custom_build_catalog> clean

Example:

$ make O=/home/hedin/prj/cpupower/build clean

Use 'DESTDIR' command line variable to uninstall previously installed files

from the given dir:

$ make DESTDIR=<your_custom_install_catalog>

Example:

make DESTDIR=/home/hedin/prj/cpupower uninstall

running the tool

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

default directory

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

$ sudo cpupower

custom directory

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

When it comes to run the utility from the custom build catalog things

become a little bit complicated as 'just run' approach doesn't work.

Assuming that the current dir is '<your_custom_install_catalog>/usr',

issuing the following command:

$ sudo ./bin/cpupower

will produce the following error output:

./bin/cpupower: error while loading shared libraries: libcpupower.so.1:

cannot open shared object file: No such file or directory

The issue is that binary cannot find the 'libcpupower' library. So, we

shall point to the lib dir:

sudo LD_LIBRARY_PATH=lib64/ ./bin/cpupower

THANKS