AC_CHECK_HEADER([linux/input.h], [:], AC_MSG_ERROR([kernel headers not found]))
AC_SUBST([INCLUDE_PREFIX], [$(echo '#include <linux/input.h>' | eval $ac_cpp -E - | sed -n '/linux\/input.h/ {s:.*"\(.*\)/linux/input.h".*:\1:; p; q}')])
AC_CHECK_HEADER([linux/input.h], [:], AC_MSG_ERROR([kernel headers not found]))
AC_SUBST([INCLUDE_PREFIX], [$(echo '#include <linux/input.h>' | eval $ac_cpp -E - | sed -n '/linux\/input.h/ {s:.*"\(.*\)/linux/input.h".*:\1:; p; q}')])