path: root/Makefile

VERSION = 2
PATCHLEVEL = 6
SUBLEVEL = 18
EXTRAVERSION = -rc4
NAME=Crazed Snow-Weasel

# *DOCUMENTATION*
# To see a list of typical targets execute "make help"
# More info can be located in ./README
# Comments in this file are targeted only to the developer, do not
# expect to learn how to build the kernel reading this file.

# Do not print "Entering directory ..."
MAKEFLAGS += --no-print-directory

# We are using a recursive build, so we need to do a little thinking
# to get the ordering right.
#
# Most importantly: sub-Makefiles should only ever modify files in
# their own directory. If in some directory we have a dependency on
# a file in another dir (which doesn't happen often, but it's often
# unavoidable when linking the built-in.o targets which finally
# turn into vmlinux), we will call a sub make in that other dir, and
# after that we are sure that everything which is in that other dir
# is now up to date.
#
# The only cases where we need to modify files which have global
# effects are thus separated out and done before the recursive
# descending is started. They are now explicitly listed as the
# prepare rule.

# To put more focus on warnings, be less verbose as default
# Use 'make V=1' to see the full commands

ifdef V
  ifeq ("$(origin V)", "command line")
    KBUILD_VERBOSE = $(V)
  endif
endif
ifndef KBUILD_VERBOSE
  KBUILD_VERBOSE = 0
endif

# Call checker as part of compilation of C files
# Use 'make C=1' to enable checking (sparse, by default)
# Override with 'make C=1 CHECK=checker_executable CHECKFLAGS=....'

ifdef C
  ifeq ("$(origin C)", "command line")
    KBUILD_CHECKSRC = $(C)
  endif
endif
ifndef KBUILD_CHECKSRC
  KBUILD_CHECKSRC = 0
endif

# Use make M=dir to specify directory of external module to build
# Old syntax make ... SUBDIRS=$PWD is still supported
# Setting the environment variable KBUILD_EXTMOD take precedence
ifdef SUBDIRS
  KBUILD_EXTMOD ?= $(SUBDIRS)
endif
ifdef M
  ifeq ("$(origin M)", "command line")
    KBUILD_EXTMOD := $(M)
  endif
endif


# kbuild supports saving output files in a separate directory.
# To locate output files in a separate directory two syntaxes are supported.
# In both cases the working directory must be the root of the kernel src.
# 1) O=
# Use "make O=dir/to/store/output/files/"
#
# 2) Set KBUILD_OUTPUT
# Set the environment variable KBUILD_OUTPUT to point to the directory
# where the output files shall be placed.
# export KBUILD_OUTPUT=dir/to/store/output/files/
# make
#
# The O= assignment takes precedence over the KBUILD_OUTPUT environment
# variable.


# KBUILD_SRC is set on invocation of make in OBJ directory
# KBUILD_SRC is not intended to be used by the regular user (for now)
ifeq ($(KBUILD_SRC),)

# OK, Make called in directory where kernel src resides
# Do we want to locate output files in a separate directory?
ifdef O
  ifeq ("$(origin O)", "command line")
    KBUILD_OUTPUT := $(O)
  endif
endif

# That's our default target when none is given on the command line
PHONY := _all
_all:

ifneq ($(KBUILD_OUTPUT),)
# Invoke a second make in the output directory, passing relevant variables
# check that the output directory actually exists
saved-output := $(KBUILD_OUTPUT)
KBUILD_OUTPUT := $(shell cd $(KBUILD_OUTPUT) && /bin/pwd)
$(if $(KBUILD_OUTPUT),, \
     $(error output directory "$(saved-output)" does not exist))

PHONY +=