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Subject: Re: [PATCH 2/6] kbuild: allow Kbuild to start from any directory
To:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        linux-kbuild@vger.kernel.org
Cc:     Michal Marek <michal.lkml@markovi.net>,
        linux-kernel@vger.kernel.org
References: <1553947458-8311-1-git-send-email-yamada.masahiro@socionext.com>
 <1553947458-8311-2-git-send-email-yamada.masahiro@socionext.com>
Reply-To: kbingham@kernel.org
From:   Kieran Bingham <kbingham@kernel.org>
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Message-ID: <ad958d87-1e1e-2790-2f7e-380d4d9d67da@kernel.org>
Date:   Tue, 2 Apr 2019 11:41:38 +0700
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Hi Yamada-san,

Thank you for the patches,

I like the direction this series is taking.

Small spelling error spotted below...
But as I've now gone through all of it I'll offer

Reviewed-by: Kieran Bingham <kbingham@kernel.org>


On 30/03/2019 12:04, Masahiro Yamada wrote:
> Kbuild always runs in the top of the output directory.
> 
> If Make starts in the source directory with O=, it relocates the
> working directory to the location specified by O=.
> 
> Also, users can start build from the output directory by using the
> Makefile generated by scripts/mkmakefile.
> 
> With a little more effort, Kbuild will be able to start from any
> directory path.
> 
> This commit allows to specify the source directory by using
> the -f option.
> 
> For example, you can do:
> 
>   $ cd path/to/output/dir
>   $ make -f path/to/source/dir/Makefile
> 
> Or, for the equivalent behavior, you can do:
> 
>   $ make O=path/to/output/dir -f path/to/source/dir/Makefile
> 
> KBUILD_SRC is now deprecated.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
>  Makefile | 87 +++++++++++++++++++++++++++++++++++++---------------------------
>  1 file changed, 50 insertions(+), 37 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 9cbd367..1b2a70e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -96,56 +96,65 @@ endif
>  
>  export quiet Q KBUILD_VERBOSE
>  
> -# 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.
> +# Kbuild will save output files in the current working directory.
> +# This does not need to match to the root of the kernel source tree.
> +#
> +# For example, you can do this:
> +#
> +#  cd /dir/to/store/output/files; make -f /dir/to/kernel/source/Makefile
> +#
> +# If you want to save output files in a different location, there are
> +# two syntaxes to specify it.
> +#
>  # 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
> +# Set the environment variable KBUILD_OUTPUT to point to the output directory.
> +# export KBUILD_OUTPUT=dir/to/store/output/files/; make
>  #
>  # The O= assignment takes precedence over the KBUILD_OUTPUT environment
>  # variable.
>  
> -# KBUILD_SRC is not intended to be used by the regular user (for now),
> -# it is set on invocation of make with KBUILD_OUTPUT or O= specified.
> -
> -# OK, Make called in directory where kernel src resides
> -# Do we want to locate output files in a separate directory?
> +# Do we want to change the working directory?
>  ifeq ("$(origin O)", "command line")
>    KBUILD_OUTPUT := $(O)
>  endif
>  
> -ifneq ($(words $(subst :, ,$(CURDIR))), 1)
> -  $(error main directory cannot contain spaces nor colons)
> +ifneq ($(KBUILD_OUTPUT),)
> +# Make's built-in functions such as $(abspath ...), $(realpath ...) cannot
> +# expand a shell special character '~'. We use a bit tredious way to handle it.

very minor, but I noticed while looking through the series ^^

s/bit tredious/somewhat tedious/


> +abs_objtree := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) && pwd)
> +$(if $(abs_objtree),, \
> +     $(error failed to create output directory "$(KBUILD_OUTPUT)"))
> +
> +# $(realpath ...) resolves symlinks
> +abs_objtree := $(realpath $(abs_objtree))
> +else
> +abs_objtree := $(CURDIR)
> +endif # ifneq ($(KBUILD_OUTPUT),)
> +
> +ifeq ($(abs_objtree),$(CURDIR))
> +# Suppress "Entering directory ..." unless we are changing the work directory.
> +MAKEFLAGS += --no-print-directory
> +else
> +need-sub-make := 1
>  endif
>  
> -ifneq ($(KBUILD_OUTPUT),)
> -# check that the output directory actually exists
> -saved-output := $(KBUILD_OUTPUT)
> -KBUILD_OUTPUT := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) \
> -								&& pwd)
> -$(if $(KBUILD_OUTPUT),, \
> -     $(error failed to create output directory "$(saved-output)"))
> +abs_srctree := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
> +
> +ifneq ($(words $(subst :, ,$(abs_srctree))), 1)
> +$(error source directory cannot contain spaces or colons)
> +endif
>  
> +ifneq ($(abs_srctree),$(abs_objtree))
>  # Look for make include files relative to root of kernel src
>  #
>  # This does not become effective immediately because MAKEFLAGS is re-parsed
> -# once after the Makefile is read.  It is OK since we are going to invoke
> -# 'sub-make' below.
> -MAKEFLAGS += --include-dir=$(CURDIR)
> -
> +# once after the Makefile is read. We need to invoke sub-make.
> +MAKEFLAGS += --include-dir=$(abs_srctree)
>  need-sub-make := 1
> -else
> -
> -# Do not print "Entering directory ..." at all for in-tree build.
> -MAKEFLAGS += --no-print-directory
> -
> -endif # ifneq ($(KBUILD_OUTPUT),)
> +endif
>  
>  ifneq ($(filter 3.%,$(MAKE_VERSION)),)
>  # 'MAKEFLAGS += -rR' does not immediately become effective for GNU Make 3.x
> @@ -155,6 +164,7 @@ need-sub-make := 1
>  $(lastword $(MAKEFILE_LIST)): ;
>  endif
>  
> +export abs_srctree abs_objtree
>  export sub_make_done := 1
>  
>  ifeq ($(need-sub-make),1)
> @@ -166,9 +176,7 @@ $(filter-out _all sub-make $(lastword $(MAKEFILE_LIST)), $(MAKECMDGOALS)) _all:
>  
>  # Invoke a second make in the output directory, passing relevant variables
>  sub-make:
> -	$(Q)$(MAKE) \
> -	$(if $(KBUILD_OUTPUT),-C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR)) \
> -	-f $(CURDIR)/Makefile $(MAKECMDGOALS)
> +	$(Q)$(MAKE) -C $(abs_objtree) -f $(abs_srctree)/Makefile $(MAKECMDGOALS)
>  
>  endif # need-sub-make
>  endif # sub_make_done
> @@ -213,16 +221,21 @@ ifeq ("$(origin M)", "command line")
>    KBUILD_EXTMOD := $(M)
>  endif
>  
> -ifeq ($(KBUILD_SRC),)
> +ifeq ($(abs_srctree),$(abs_objtree))
>          # building in the source tree
>          srctree := .
>  else
> -        ifeq ($(KBUILD_SRC)/,$(dir $(CURDIR)))
> +        ifeq ($(abs_srctree)/,$(dir $(abs_objtree)))
>                  # building in a subdirectory of the source tree
>                  srctree := ..
>          else
> -                srctree := $(KBUILD_SRC)
> +                srctree := $(abs_srctree)
>          endif
> +
> +	# TODO:
> +	# KBUILD_SRC is only used to distinguish in-tree/out-of-tree build.
> +	# Replace it with $(srctree) or something.
> +	KBUILD_SRC := $(abs_srctree)
>  endif
>  
>  export KBUILD_CHECKSRC KBUILD_EXTMOD KBUILD_SRC
> 


-- 
--
Kieran