linux-kernel - Re: [PATCH 1/3] handling of

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Message-ID: <20141001181533.GB13544@opentech.at>
Date:	Wed, 1 Oct 2014 20:15:33 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Randy Dunlap <rdunlap@...radead.org>
Cc:	Michal Marek <mmarek@...e.cz>,
	Christoph Hellwig <hch@...radead.org>,
	Joe Perches <joe@...ches.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] handling of _shipped files

On Wed, 01 Oct 2014, Randy Dunlap wrote:

> On 10/01/14 06:36, Nicholas Mc Guire wrote:
> > 
> > handling of _shipped files
> > 
> > This adds a section on handling of _shipped files in kbuild
> > Makefiles and the build process.
> > 
> > Signed-off-by: Nicholas Mc Guire <der.herr@...r.at>
> > ---
> >  Documentation/kbuild/makefiles.txt |   57 +++++++++++++++++++++++++++++++++++-
> >  1 file changed, 56 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
> > index 764f599..d0bd91a 100644
> > --- a/Documentation/kbuild/makefiles.txt
> > +++ b/Documentation/kbuild/makefiles.txt
> > @@ -19,6 +19,7 @@ This document describes the Linux kernel Makefiles.
> >  	   --- 3.10 Special Rules
> >  	   --- 3.11 $(CC) support functions
> >  	   --- 3.12 $(LD) support functions
> > +	   --- 3.13 _shipped - generated files
> >  
> >  	=== 4 Host Program support
> >  	   --- 4.1 Simple Host Program
> > @@ -595,6 +596,60 @@ more details, with real examples.
> >  		LDFLAGS_vmlinux += $(call ld-option, -X)
> >  
> >  
> > +--- 3.13 _shipped - generated files
> > +
> > +   Some sources in the kernel are generated by tools or special
> > +   purpose scrips so that the build process dependencies can be kept
> 
>               scripts
> 
> > +   at a resonable level. Also in cases where the translation is not
> 
>            reasonable
>  
> > +   configuration dependent but might impact build time _shipped files
> 
>                                                build time,
> 
> > +   may be added along with the actual sources to speed up the build
> > +   process.
> > +
> > +   For standard tools like lex and yacc the make process will actually
> > +   generate the _shipped files (see scripts/Makefile.lib) and retain
> > +   them by marking them .PRECIOUS so they are not removed by the clean
> > +   targets.
> > +
> > +   For non standard tools the generation of the _shipped file it self
> 
>           non-standard                                           itself
> 
> > +   may be manually achived by building and then renaming. A makefile
> 
>                       achieved
> 
> > +   target for generate the actual target file should to be provided
> 
>              to generate
> 
> > +   though and can be conditioned on an environment variable.
> 
> Most examples that I see just expect the Makefile to be modified to set
> (or define) the variable.
>

Yes - but is that the prefered way of doing it ? I guess it
would be more clear to have a variable that is taken from the
environment and not via .config to trigger a conditional rebuild
as the defkeymap example does it.
 
> > +
> > +	Example:
> > +		ifdef GENERATE_KEYMAP
> > +
> > +		$(obj)/defkeymap.c: $(obj)/%.c: $(src)/%.map
> > +			loadkeys --mktable $< > $@
> > +
> > +		endif
> > +
> > +   The _shipped file does not appear in the actual Makefile, this is
> > +   handled by the rules found in scripts/Makefile.lib.
> > +
> > +		<snip>
> > +		cmd_shipped = cat $< > $@
> > +
> > +		$(obj)/%: $(src)/%_shipped
> > +			$(call cmd,shipped)
> > +		<snip>
> > +
> > +   which simply will copy the target_shipped to the target
> > +
> > +   If a file of a make target is found in the build directory with the
> > +   extension _shipped make will used it, rather than generating the
> 
>                 _shipped, make will use it rather than generating the
> 
> > +   respective target file from source.
> > +
> > +   The build will indicate the use of the _shipped file by the SHIPPED
> > +   quiet command in the make output.
> > +
> > +	Example:
> > +		LD      drivers/scsi/aic7xxx/built-in.o
> > +		SHIPPED drivers/scsi/aic7xxx/aic79xx_seq.h
> > +		SHIPPED drivers/scsi/aic7xxx/aic79xx_reg.h
> > +		CC [M]  drivers/scsi/aic7xxx/aic79xx_core.o
> > +		CC [M]  drivers/scsi/aic7xxx/aic79xx_pci.o
> > +		SHIPPED drivers/scsi/aic7xxx/aic79xx_reg_print.c
> > +		CC [M]  drivers/scsi/aic7xxx/aic79xx_reg_print.o
> >  === 4 Host Program support
> >  
> >  Kbuild supports building executables on the host for use during the
> > @@ -1423,10 +1478,10 @@ Original version made by Michael Elizabeth Chastain, <mailto:mec@...ut.net>
> >  Updates by Kai Germaschewski <kai@....ruhr-uni-bochum.de>
> >  Updates by Sam Ravnborg <sam@...nborg.org>
> >  Language QA by Jan Engelhardt <jengelh@....de>
> > +Kbuild support for shipped files Nicholas Mc Guire <der.herr@...r.at>
> >  
> >  === 11 TODO
> >  
> > -- Describe how kbuild supports shipped files with _shipped.
> >  - Generating offset header files.
> >  - Add more variables to section 7?
> >  
> > 
>
and thanks for the language fixes - thought I had spellchecked it but 
obviously I did not 

thx!
hofrat 
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