#!/bin/bash

########################
# Function definitions #
########################

# First three components of the kernel version number.
function kernel_version {
  echo "$1" | sed -n 's/^\([0-9]*\.[0-9]*\.[0-9]*\).*$/\1/p'
}

# Last component of the kernel version, or the empty string if $1 has only
# three components.
function patchlevel {
  echo "$1" | sed -n 's/^\([0-9]*\.[0-9]*\.[0-9]*\)[.-]\(.*\)$/\2/p'
}

# Create a linux-$1 tree in the current directory, where $1 is a kernel
# version number with either three or four components.
function extract_kernel_tree {
  local kver="$(kernel_version $1)"
  local plevel="$(patchlevel $1)"
  local tmpdir=kernel-tree-tmp-$$

  rm -rf "linux-$1" "${tmpdir}"
  mkdir "${tmpdir}" || return $?
  (
    cd "${tmpdir}" || return $?
    tar xjf "${kernel_sources}/linux-${kver}.tar.bz2" || return $?
    cd "linux-${kver}" || return $?
    if [ "${plevel}" != "" ]; then
      bzip2 -cd "${kernel_sources}/patch-$1.bz2" \
        | patch -p1 -f -s || return $?
    fi
    cd ..
    mv "linux-${kver}" "../linux-$1" || return $?
  )
  rmdir "${tmpdir}"
}

# Download the file from URL $1 and save it in the current directory.
function download_file {
  if [ ! -e "$(basename "$1")" ]; then
    if [ "${quiet_download}" = "false" ]; then
      echo "Downloading $1 ..."
    fi
    if ! wget -q -nc "$1"; then
      echo "Downloading $1 failed."
      return 1
    fi
  fi
}

# Make sure the kernel tarball and patch file are present in directory
# ${kernel_sources}. Download any missing files from ${kernel_mirror}.
function download_kernel {
  local kver="$(kernel_version $1)"
  local plevel="$(patchlevel $1)"

  mkdir -p "${kernel_sources}" || return $?
  test -w "${kernel_sources}" || return $?
  (
    cd "${kernel_sources}" || return $?
    download_file "${kernel_mirror}/linux-$(kernel_version $1).tar.bz2" \
      || return $?
    if [ "${plevel}" != "" ]; then
      download_file "${kernel_mirror}/patch-$1.bz2" || return $?
    fi
  )
}


#########################
# Argument verification #
#########################

# Where to store persistenly downloaded kernel tarballs and kernel patches.
kernel_sources="$HOME/software/downloads"
# URL for downloading kernel tarballs and kernel patches.
kernel_mirror="ftp://ftp.eu.kernel.org/pub/linux/kernel/v2.6"

kernel_version="$1"

if [ "$1" = "" ]; then
  echo "Error: missing kernel version argument."
  exit 1
fi

mkdir -p qla2xxx-orig
cd qla2xxx-orig || exit $?
extract_kernel_tree "${kernel_version}"
touch linux-*/drivers/scsi/qla2xxx/*
rm -rf "${kernel_version}"
mkdir -p "${kernel_version}"
mv linux-*/drivers/scsi/qla2xxx/* "${kernel_version}"
rm -rf linux-*
cd ..