3.6. Working with ELDK

After the initial installation is complete, all you have to do to start working with the ELDK is to set and export the CROSS_COMPILE environment variable. Optionally, you may wish to add the bin and usr/bin directories of your ELDK installation to the value of your PATH environment variable. For instance, a sample ELDK installation and usage scenario looks as follows:

• Create a new directory where the ELDK is to be installed, say:

  bash$ mkdir /opt/eldk
  

• Mount a CD or an ISO image with the distribution:

  bash$ mount /dev/cdrom /mnt/cdrom
  

• Run the installation utility included on the distribution to install into that specified directory:

  bash$ /mnt/cdrom/install -d /opt/eldk
  

• After the installation utility completes, export the CROSS_COMPILE variable:

     bash$ export CROSS_COMPILE=ppc_4xxFP-
     

• The trailing '-' character in the CROSS_COMPILE variable value is optional and has no effect on the cross tools behavior. However, it is required when building Linux kernel and U-Boot images.

• Add the directories /opt/eldk/usr/bin and /opt/eldk/bin to PATH:

  bash$ PATH=$PATH:/opt/eldk/usr/bin:/opt/eldk/bin
  

• Compile a file:

  bash$ ${CROSS_COMPILE}gcc -o hello_world hello_world.c
  

  You can also call the cross tools using the generic prefix ppc-linux- for example:

  bash$ ppc-linux-gcc -o hello_world hello_world.c
  

• or, equivalently:

  bash$ /opt/eldk/usr/ppc-linux/bin/gcc -o hello_world hello_world.c                                                                               
  

The value of the CROSS_COMPILE variable must correspond to the target CPU family you want the cross tools to work for. Refer to the table below for the supported CROSS_COMPILE variable values:

3.6.A Table of possible values for $CROSS_COMPILE

CROSS_COMPILE Value	Predefined Compiler Flag	FPU present or not
ppc_4xx-	-mcpu=403	No
ppc_4xxFP-	-mcpu=405fp	Yes
ppc_6xx-	-mcpu=603	Yes
ppc_74xx-	-mcpu=7400	Yes
ppc_8xx-	-mcpu=860	No
ppc_85xx-	-mcpu=8540	Yes
ppc64-linux-	-mcpu=powerpc64	Yes

For compatibility with older versions of the ELDK and with other toolkits the following values for $CROSS_COMPILE can be used, too: ppc_7xx- and ppc_82xx-. These are synonyms for ppc_6xx.

3.6.1. Switching Between Multiple Installations

No special actions are required from the user to switch between multiple ELDK installations on the same host system. Which ELDK installation is used is determined entirely by the filesystem location of the binary that is being invoked. This approach can be illustrated using the following example.

Assume the directory /work/denx_tools/usr/bin, where the ppc-linux-gcc compiler binary has been installed, is a part of the PATH environment variable. The user types the command as follows:

$ ppc_8xx-gcc -c myfile.c

To load the correct include files, find the correct libraries, spec files, etc., the compiler needs to know the ELDK root directory. The compiler determines this information by analyzing the shell command it was invoked with ( ppc_8xx-gcc - without specifying the explicit path in this example) and, if needed, the value of the PATH environment variable. Thus, the compiler knows that it has been executed from the /work/denx_tools/usr/bin directory.

Then, it knows that the compiler is installed in the usr/bin subdirectory of the root installation directory, so the ELDK, the compiler is a part of, has been installed in the subdirectories of the /work/denx_tools directory. This means that the target include files are in /work/denx_tools/<target_cpu_variant>/usr/include, and so on.

3.5.5. Removal of the Entire Installation		1. Abstract		3.7. Mounting Target Components via NFS
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