>>> Emerging (1 of 2) net-wireless/ieee80211-1.2.15 to /
 * ieee80211-1.2.15.tgz MD5 ;-) ...                                                                                                                                   [ ok ]
 * ieee80211-1.2.15.tgz RMD160 ;-) ...                                                                                                                                [ ok ]
 * ieee80211-1.2.15.tgz SHA1 ;-) ...                                                                                                                                  [ ok ]
 * ieee80211-1.2.15.tgz SHA256 ;-) ...                                                                                                                                [ ok ]
 * ieee80211-1.2.15.tgz size ;-) ...                                                                                                                                  [ ok ]
 * checking ebuild checksums ;-) ...                                                                                                                                  [ ok ]
 * checking auxfile checksums ;-) ...                                                                                                                                 [ ok ]
 * checking miscfile checksums ;-) ...                                                                                                                                [ ok ]
 * checking ieee80211-1.2.15.tgz ;-) ...                                                                                                                              [ ok ]
 * Determining the location of the kernel source code
 * Found kernel source directory:
 *     /usr/src/linux
 * Could not find a usable .config in the kernel source directory.
 * Please ensure that /usr/src/linux points to a configured set of Linux sources.
 * If you are using KBUILD_OUTPUT, please set the environment var so that
 * it points to the necessary object directory so that it might find .config.

!!! ERROR: net-wireless/ieee80211-1.2.15 failed.
Call stack:
  ebuild.sh, line 1629:   Called dyn_setup
  ebuild.sh, line 701:   Called qa_call 'pkg_setup'
  ebuild.sh, line 38:   Called pkg_setup
  ieee80211-1.2.15.ebuild, line 37:   Called linux-mod_pkg_setup
  linux-mod.eclass, line 458:   Called linux-info_pkg_setup
  linux-info.eclass, line 554:   Called die

!!! Unable to calculate Linux Kernel version
!!! If you need support, post the topmost build error, and the call stack if relevant.
!!! A complete build log is located at '/var/tmp/portage/net-wireless/ieee80211-1.2.15/temp/build.log'.