CONFIG.MK analysis of Uboot top layer

#
# (C) Copyright 2000-2006
# Wolfgang Denk, DENX software Engineering, [email protected]
#
# See file CREDITS for list of people who contributed to this
# project.
#
# is the free software; You can redistribute it and/or
# Modify it under the terms of the GNU general public License as
# published by the free software Foundation; Either version 2 of
# The License, or (at your option) any later version.
#
# distributed in the hope that it'll be useful,
# but without any WARRANTY; Without even the implied warranty of
# merchantability or FITNESS for A particular PURPOSE. See the
# GNU general public License for more details.
#
# You should has received a copy of the GNU general public License
# along with the program; If not, write to the free software
# Foundation, Inc., Temple Place, Suite Boston,
# MA 02111-1307 USA
#

#########################################################################

Ifneq ($ (Objtree), $ (srctree))
Ifeq ($ (CURDIR), $ (srctree))
Dir: =
Else
Dir: = $ (subst $ (srctree)/,,$ (CURDIR))
endif

OBJ: = $ (if $ (dir), $ (objtree)/$ (dir)/,$ (objtree)/)
SRC: = $ (if $ (dir), $ (srctree)/$ (dir)/,$ (srctree)/)

$ (Shell mkdir-p $ (obj))
Else
Obj: =
SRC: =
endif

# Clean the slate ...
Platform_relflags =
Platform_cppflags =
Platform_ldflags =

#########################################################################

Ifeq ($ (Hostos), Darwin)
hostcc= cc
Else
hostcc= GCC
endif
hostcflags=-wall-wstrict-prototypes-o2-fomit-frame-pointer
hoststrip= Strip

#########################################################################
#
# Option Checker (courtesy Linux kernel) to ensure
# only supported compiler options is used
#
Cc-option = $ (Shell if $ (CC) $ (CFLAGS) $ (1)-s-o/dev/null-xc/dev/null \
>/dev/null 2>&1; Then echo "$ (1)"; else echo "$ (2)"; Fi;)

#
# Include The Make variables (CC, etc ...)

#相关的编译文件
#
As= $ (cross_compile) as
Ld= $ (cross_compile) LD
Cc= $ (cross_compile) gcc
Cpp= $ (CC)-E
Ar= $ (cross_compile) AR
Nm= $ (cross_compile) NM
Ldr= $ (cross_compile) LDR
Strip= $ (cross_compile) STRIP
Objcopy = $ (cross_compile) objcopy
OBJDUMP = $ (cross_compile) OBJDUMP
Ranlib= $ (cross_compile) Ranlib

#########################################################################

# Load Generated Board configuration
Sinclude $ (objtree)/include/autoconf.mk

Ifdefarch
Sinclude $ (Topdir)/lib_$ (ARCH)/config.mk# include architecture dependend rules
endif
Ifdefcpu
Sinclude $ (Topdir)/cpu/$ (CPU)/config.mk# include cpuspecific rules
endif
Ifdefsoc
Sinclude $ (Topdir)/cpu/$ (CPU)/$ (SOC)/config.mk# include socspecific rules
endif
Ifdefvendor
Boarddir = $ (VENDOR)/$ (BOARD)
Else
Boarddir = $ (BOARD)
endif
Ifdefboard
Sinclude $ (Topdir)/board/$ (boarddir)/config.mk# include board specific rules
endif

#########################################################################

IFNEQ (, $ (findstring s,$ (makeflags)))//In $ (makeflags) Find out if there is an S character
Arflags = CR//Don't quite understand the meaning of these two items
Else
Arflags = CRV
endif
Relflags= $ (platform_relflags)
Dbgflags=-G #-ddebug Debug Options
optflags=-os #-fomit-frame-pointer Optimization options
Ifndef Ldscript
#LDSCRIPT: = $ (Topdir)/board/$ (boarddir)/u-boot.lds.debug
Ifeq ($ (config_nand_u_boot), y)
Ldscript: = $ (Topdir)/board/$ (boarddir)/u-boot-nand.lds
Else
Ldscript: = $ (Topdir)/board/$ (boarddir)/u-boot.lds
endif
endif
Objcflags + =--gap-fill=0xff

Gccincdir: = $ (Shell $ (CC)-print-file-name=include)

Cppflags: = $ (dbgflags) $ (optflags) $ (relflags) \
-d__kernel__

Ifneq ($ (boot_media),)
Boot_media_macro = boot_media_$ (Shell echo $ (Boot_media) | tr ' [A-z] ' [A-z] ')
Cppflags + =-d$ (Boot_media_macro)
endif

Ifneq ($ (text_base),)
Cppflags + =-dtext_base=$ (text_base)
endif

Ifneq ($ (Objtree), $ (srctree))
Cppflags + =-i$ (objtree)/include2-i$ (objtree)/include
endif

Cppflags + =-i$ (topdir)/include
Cppflags + =-fno-builtin-ffreestanding-nostdinc\
-isystem $ (Gccincdir)-pipe $ (platform_cppflags)

Ifdef Build_tag
CFLAGS: = $ (cppflags)-wall-wstrict-prototypes \
-dbuild_tag= ' "$ (build_tag)" '
Else
CFLAGS: = $ (cppflags)-wall-wstrict-prototypes
endif

CFLAGS + = $ (call cc-option,-fno-stack-protector)

# Avoid trigraph warnings while parsing pci.h (produced by NIOS gcc-2.9)
# This option has to been placed Behind-wall--that's why it's here
Ifeq ($ (ARCH), Nios)
Ifeq ($ (findstring 2.9,$ (Shell $ (CC)--version)), 2.9)
CFLAGS: = $ (cppflags)-wall-wno-trigraphs
endif
endif

# $ (cppflags) sets-g, which causes GCC to pass a suitable-g<format>
# option to the assembler.
Aflags_debug: =

# turn JBSR into JSR for m68k
Ifeq ($ (ARCH), m68k)
Ifeq ($ (findstring 3.4,$ (Shell $ (CC)--version)), 3.4)
Aflags_debug: =-wa,-gstabs,-s
endif
endif

Aflags: = $ (Aflags_debug)-d__assembly__ $ (cppflags)

Ldflags + =-bstatic-t $ (obj) U-boot.lds $ (platform_ldflags)
Ifneq ($ (text_base),)
Ldflags + =-ttext $ (text_base)
endif

# location of a usable BFD library, where we define "usable" as
# "Built for ${host}, supports ${target}". Sensible values are
#-When cross-compiling:the root of the cross-environment
#-LINUX/PPC (native):/usr
#-NETBSD/PPC (native): You lose ... (must extract these from the
# binutils build directory, plus the native and u-boot include
# files don ' t like all other)
#
# So far, this is used only by Tools/gdb/makefile.

Ifeq ($ (Hostos), Darwin)
Bfd_root_dir =/usr/local/tools
Else
Ifeq ($ (Hostarch), $ (ARCH))
# native
Bfd_root_dir =/USR
Else
#BFD_ROOT_DIR =/linuxppc/cdk# linux/i386
#BFD_ROOT_DIR =/usr/pkg/cross# netbsd/i386
Bfd_root_dir =/OPT/POWERPC
endif
endif

#########################################################################

EXPORTHOSTCC hostcflags cross_compile \
As LD CC CPP AR NM STRIP objcopy OBJDUMP make
Exporttext_base platform_cppflags platform_relflags cppflags CFLAGS aflags

#########################################################################

# Allow boards to use custom optimize flags on a per dir/file basis
Bcurdir: = $ (Notdir $ (CURDIR))
$ (obj)%.s:%. S
$ (CPP) $ (aflags) $ (aflags_$ (@F)) $ (aflags_$ (bcurdir))-o [email protected] $<
$ (obj)%.o:%. S
$ (CC) $ (aflags) $ (aflags_$ (@F)) $ (aflags_$ (bcurdir))-o [email protected] $<-C
$ (obj)%.o:%.c
$ (CC) $ (CFLAGS) $ (cflags_$ (@F)) $ (cflags_$ (bcurdir))-o [email protected] $<-C
$ (obj)%.i:%.c
$ (CPP) $ (CFLAGS) $ (cflags_$ (@F)) $ (cflags_$ (bcurdir))-o [email protected] $<-C
$ (obj)%.s:%.c
$ (CC) $ (CFLAGS) $ (cflags_$ (@F)) $ (cflags_$ (bcurdir))-o [email protected] $<-c-s

#########################################################################

CONFIG.MK analysis of Uboot top layer