dkms-3

слегка перепилил 2-ой вариант
добавил проверку последнего изменения базы dkms и базы пакетов
если база пакетов изменилась позже, то пересоздать dkms_db
т.к. проверка такая быстрей, нежели пересоздание базы

echo 3 > /proc/sys/vm/drop_caches
time stat -c %Y ${DB}*/ ${DB}*/*/ | sort | tail -n1 
1333457079

real 0m1.903s
user 0m0.027s
sys 0m0.000s

супротив

echo 3 > /proc/sys/vm/drop_caches
time dkms-gentoo --db                                                                                                        [ ok ]

real 0m19.250s
user 0m0.143s
sys 0m0.010s

ну и вот что получилось

#!/bin/bash

. /etc/init.d/functions.sh

DB="/var/db/pkg/"
KERNEL="$(uname -r)"
DKMS_DB="/var/lib/portage/dkms_db"

case ${1} in

--check ) check(){
  if [ -f "${DKMS_DB}" ];then
 while read PKG MOD PKG_FILE;do
   MOD_FILE="/lib/modules/${KERNEL}/${MOD}"
   if [ -f "${MOD_FILE}" ];then
##### version of current_kernel's module
  MOD_VER="$( modinfo "${MOD_FILE}" | awk '/^version/ {print $2}' )"
##### version of pkg's module
  PKG_VER="$( modinfo "${PKG_FILE}" | awk '/^version/ {print $2}' )"
  if [ "${PKG_VER}" != "${MOD_VER}" ];then
    FAILED+=" ${PKG}" 
    echo "${MOD#*/}" && eend 1
  else
    echo "${MOD#*/}" && eend 0
  fi
   else
  FAILED+=" ${PKG}" 
  echo "${MOD#*/}" && eend 1
   fi
 done < ${DKMS_DB}
 if [ -n "${FAILED}" ];then
##### rebuilding broken modules for current kernel
   eselect kernel set linux-${KERNEL}
   emerge -1 $(echo -e "${FAILED// /\n}" | sort -u) \
   && rm -f /var/tmp/dkms_failed \
   || touch /var/tmp/dkms_failed
 fi
  else
 echo -e "dkms_db not found!\nyou need run:\ndkms-gentoo --db" && return 1
  fi
  }
  check;;

--db ) db_rebuild(){

  db_create(){
##### list of all installed modules by packages
  TARGETS="$(grep "/lib/modules/.*.ko\>" ${DB}*/*/CONTENTS)"
  while read line;do
 MODULE="$(awk '{print $2}' <<< ${line})"
 KO="${MODULE#/*/*/*/}"
 PKG_FULL="${line%/CONTENTS*}"
##### get ${CATEGORY}/${PN}
 export "$(bzgrep "declare -x CATEGORY=" ${PKG_FULL}/environment.bz2 | awk '{print $3}')"
 export "$(bzgrep "declare -x PN=" ${PKG_FULL}/environment.bz2 | awk '{print $3}')"
##### creating database
 DATA+="${CATEGORY//'"'/}/${PN//'"'/} ${KO} ${MODULE}\n"
  done <<< "${TARGETS}"
 echo -e "${DATA%\\n}" | column -t > ${DKMS_DB}
  eend 0
  }

  if [ -f "${DKMS_DB}" ];then
##### rebuild db if dkms's database older then pkg's database
 DKMS_TIMESTAMP="$(stat -c %Y ${DKMS_DB})"
 DB_TIMESTAMP="$(stat -c %Y ${DB}*/ ${DB}*/*/ | sort | tail -n1)"
 if (( "${DB_TIMESTAMP}" > "${DKMS_TIMESTAMP}" ));then
   db_create
   eend $?
 else
   eend 0
 fi
  else
 db_create
 eend $?
  fi
  }
  db_rebuild;;

--list )
  if [ -f "${DKMS_DB}" ];then
 awk '{print $1,$2}' ${DKMS_DB} | column -t
  else
 echo "database not found!"
  fi;;

* ) echo \
"Usage: dkms-gentoo [option]
available options:
--db     rebuild database.
--list   display database.
--check  check modules.";;

esac