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资源说明：uClinux for LEON3 modified in the Universidad Distrital Francisco Jóse de Caldas
SnapGear Embedded Linux Distribution
====================================
Contents
--------
0. Introduction
1. Instructions for compiling
2. Changing the applications/kernel-options/libraries
3. Documentation
0. Introduction
---------------
The SnapGear Embedded Linux Distribution is a source package for building
complete, ready to run binary images for embedded Linux systems. It contains
Linux kernels, libraries and a huge application set that can be easily
configured and built for a wide varity of embedded targets.
1. Instructions for Compiling
-----------------------------
1. You will need a cross-compiler package for your target. Many binary
tools packages exists specifically for compiling this source
distribution. Install that in the standard way first. For example, if
you are targeting m68k or ColdFire systems then you can use the
m68k-elf-tools binary packages from www.snapgear.org.
2. If you have not un-archived the source package then do that now.
It is a gziped tar image, so do:
tar xvzf snapgear-XXXXXXXX.tar.gz
This will dump the source into a "snapgear" directory. You can do
this into any directory, typically use your own user login. (I don't
recommend devloping as root, it is a bad pactice, and it will bite
you one day!)
3. Cd into the source tree:
cd snapgear
4. Configure the build target:
make xconfig
You can also use "make config" or "make menuconfig" if you prefer.
The top level selection is straight forward if you know the vendor of
the board you want to compile for. You can choose also to modify the
underlying default kernel and application configuration if you want.
At first it is suggested that you use the default configuration for
your target board. It will almost certainly work "as is".
You can also select between different kernel versions and libraries,
at this top level. Not all kernel versions support all boards, as a
general rule choose 2.4.x. Also typically you would use glibc only on
target processors that support virtual memory (x86, SH4, XSCALE).
Most MMUless processors use uC-libc. If you choose a combination that
doesn't have a default configuration file then the xconfig step will
issue a message letting you know.
Based on what platform you choose in this step the build will generate
an appropriate default application set.
Sometimes a number of questions will appear after you 'Save and Exit'.
Do not be concerned, it just means that some new config options have
been added to the source tree that do not have defaults for the
configuration you have chosen. If this happens the safest option is
to answer 'N' to each question as they appear.
5. Build the dependencies:
make dep
6. Build the image:
make
Thats it!
The make will generate appropriate binary images for the target hardware
specified. All generated files will be placed under the "images" directory.
The exact files vary from target to target, typically you end up with
something like an "image.bin" file.
How to load and run the generated image will depend on your target system
hardware. There are a number of HOWTO documents under the Documentation
directy that describe how to load and run the image on specific boards.
Look for a file named after your target board.
2. Changing the Applications/Kernel/Libraries
---------------------------------------------
You can modify the kernel configuration and application set generated for
your target using the config system. You can configure by running one of
the following three commands:
make xconfig - graphical X11 based config
make menuconfig - text menu based config
make config - plain text shell script based config
Xconfig is by far the simplest to use, I would reccomend using that
if you can.
The key options under the "Target Platform Selection" menu are the
following:
Customize Kernel Settings
Selecting this option run the standard Linux kernel config.
Customize Vendor/User Settings
Selecting this option will run a configure process allowing
you to enable or disable individual applications and libraries.
Use the online "Help" if unsure of what a configuration option means.
When you 'Save and Exit' the build system will run you through the
configs you have selected to customise.
3. Documention
--------------
There is an assortment of documentaion files under the Documentaion
directory. The more interresting ones are:
SOURCE -- file at the top level gives a brief run down of the
structure of this source distribution package.
Documentation/Adding-User-Apps-HOWTO
-- description of how to add a new application into the
config and build setup of the distribution.
Documentation/Adding-Platforms-HOWTO
-- description of how to add a new vendor board config to
the distribution.
Documentation/-HOWTO
-- describes building and loading for a particular board.
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