The Diff Ninjutsu

Sometimes patches for certain source code which are distributed by programmers, are not in the form of the usual patch like linux kernel patches (either incremental or against the base version) which you can apply by just using the patch utility in *nix. This can cause months of headache for maintainer or someone who come later. This is where utility like diff comes handy. Let's see how to use it effectively.

First, examine the entire directory structure of the different version of the source code

diff -q -r <orig_dir> <new_dir>

Second, examine the differences between different version of certain file of interest.

diff <path_to_orig_file> <path_to_new_file>

Third, create a shell script to do the real patching. For example:

#!/bin/bash
#
# Script to apply patches to Realtek v1.4 ADK, SDK and CMK in order to 
# upgrade it to version 1.4c (with latest v1.4c patches)
# 
# Author: Darmawan Salihun
# 
#

##### ASSUMPTIONS a.k.a PRECONDITION ####################################
#
# The following directories must have been decompressed prior to the 
# execution of this script!
#
# RTL8186_LINUX_DIR="../rtl8186-sdk-1.4/rtl8186-linux-1.4"
# RTL8186_ASP_DIR="../rtl8186-adk-1.4/rtl8186-ASP-1.4"
# PATCH_1_4b_ADK="rtl8186-cmk-1.4b/patch/ADK"
# PATCH_1_4b_SDK="rtl8186-cmk-1.4b/patch/SDK"
# PATCH_1_4c_ADK_DIR="rtl8186-cmk-1.4c-release/patch/ADK"
# PATCH_1_4c_SDK_DIR="rtl8186-cmk-1.4c-release/patch/SDK"
# CMK_1_4c_PATCH_DIR="patch/files"
# CMK_1_4c_CONFIG_DIR="rtl8186-cmk-1.4c-release/config"
#
#########################################################################


# directories definition
PATCH_1_4b_ADK="rtl8186-cmk-1.4b/patch/ADK/*"
PATCH_1_4b_SDK="rtl8186-cmk-1.4b/patch/SDK/*"
PATCH_1_4c_ADK_DIR="rtl8186-cmk-1.4c-release/patch/ADK"
PATCH_1_4c_SDK_DIR="rtl8186-cmk-1.4c-release/patch/SDK"
RTL8186_ASP_DIR="../rtl8186-adk-1.4/rtl8186-ASP-1.4"
RTL8186_LINUX_DIR="../rtl8186-sdk-1.4/rtl8186-linux-1.4"
CMK_1_4c_PATCH_DIR="patch/files"
CMK_1_4c_CONFIG_DIR="rtl8186-cmk-1.4c-release/config"
CMK_1_4c_LINUX_TOOLS="rtl8186-cmk-1.4c-release/tools/LINUX/tools.tar.gz"
SDK_TOOLCHAIN="../rtl8186-sdk-1.4/rtl8186-toolchain-1.0.tar.gz"
SDK_BOOTCODE=" ../rtl8186-sdk-1.4/rtl8186-btcode-1.4a.tar.gz"
ANTEK_RTL_SDK_DIR="antek-rtl8186-sdk"

# Guard against error during execution
set -e

# step 1: upgrade ADK and SDK v1.4 to v1.4b
cp -r -v --remove-destination $PATCH_1_4b_ADK   $RTL8186_ASP_DIR 
cp -r -v --remove-destination $PATCH_1_4b_SDK   $RTL8186_LINUX_DIR 

# step 2: patch _the ADK and SDK v1.4c patch files_ with latest patches
cp -v --remove-destination $CMK_1_4c_PATCH_DIR/wireless_ag_net.o  $PATCH_1_4c_SDK_DIR/linux-2.4.18/rtl8186 
cp -v --remove-destination $CMK_1_4c_PATCH_DIR/ieee802_mib.h  $PATCH_1_4c_ADK_DIR/linux-2.4.18/drivers/net/wireless_ag

cp -v --remove-destination $CMK_1_4c_PATCH_DIR/ieee802_mib.h  $PATCH_1_4c_SDK_DIR/linux-2.4.18/drivers/net/wireless_ag

cp -v --remove-destination $CMK_1_4c_PATCH_DIR/rtl8186.tar.gz  $PATCH_1_4c_SDK_DIR/linux-2.4.18

cp -v --remove-destination $CMK_1_4c_PATCH_DIR/mkimg  $PATCH_1_4c_ADK_DIR/AP

# step 3: upgrade ADK and SDK v1.4b to v1.4c_with_latest_patches
#
#  Note: Watch for the "/*" because the paths are only _directory paths_. 
#        That's why ypu have to append them with an "/*" to ensure you don't break 
#        the directory structure of the ADK/SDK and that you replace the right 
#        files and directories.
#
cp -r -v --remove-destination $PATCH_1_4c_ADK_DIR/*  $RTL8186_ASP_DIR 
cp -r -v --remove-destination $PATCH_1_4c_SDK_DIR/*  $RTL8186_LINUX_DIR

# step 4 create Antek RTL8186 SDK from patched ADK, SDK and CMK
rm -rf $ANTEK_RTL_SDK_DIR
mkdir $ANTEK_RTL_SDK_DIR

cp -rf $RTL8186_ASP_DIR/AP  $ANTEK_RTL_SDK_DIR
cp -rf $RTL8186_LINUX_DIR/linux-2.4.18  $ANTEK_RTL_SDK_DIR

mkdir -v $ANTEK_RTL_SDK_DIR/tool 
cp -rvf  $CMK_1_4c_CONFIG_DIR   $ANTEK_RTL_SDK_DIR/tool 
tar xvzf $CMK_1_4c_LINUX_TOOLS  -C $ANTEK_RTL_SDK_DIR/tool/ 

cp -vf  $SDK_TOOLCHAIN   $ANTEK_RTL_SDK_DIR/tool 
cp -vf  $SDK_BOOTCODE   $ANTEK_RTL_SDK_DIR/tool 

# inform that we're done
echo "Realtek RTL8186 SDK v1.4c installed."

Next, you can do the first step to examine whether you have applied the patch correctly.
Actually, analysis of the patching result can be automated with shell script as well. But, let's leave it for another installment of this diff series of tutorial.

That's it for now. Ciao.

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