linux-kernel - Re: [PATCH] kbuild: get rid of misleading $(AS) from documents

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Date:   Thu, 27 Jun 2019 22:37:40 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-kbuild@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sam Ravnborg <sam@...nborg.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Michal Marek <michal.lkml@...kovi.net>
Subject: Re: [PATCH] kbuild: get rid of misleading $(AS) from documents

On Fri, Jun 28, 2019 at 11:04:33AM +0900, Masahiro Yamada wrote:
> The assembler files in the kernel are *.S instead of *.s, so they must
> be preprocessed. Hence, we always use $(CC) as an assembler driver.
> 
> $(AS) is almost unused in Kbuild. As of writing, there is just one user.
> 
>   $ git grep '$(AS)' -- :^Documentation
>   drivers/net/wan/Makefile:  AS68K = $(AS)
> 
> The documentation about *_AFLAGS* sounds like the flags were passed
> to $(AS). This is somewhat misleading since we do not invoke $(AS)
> directly.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

I did notice this when I grepped for $(AS) in the tree. Certainly makes
sense and looks good to me.

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

> ---
> 
>  Documentation/kbuild/kbuild.txt    |  5 ++---
>  Documentation/kbuild/makefiles.txt | 12 ++++++------
>  2 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt
> index 9c230ea71963..7a7e2aa2fab5 100644
> --- a/Documentation/kbuild/kbuild.txt
> +++ b/Documentation/kbuild/kbuild.txt
> @@ -31,12 +31,11 @@ Additional options to the assembler (for built-in and modules).
>  
>  AFLAGS_MODULE
>  --------------------------------------------------
> -Additional module specific options to use for $(AS).
> +Additional module specific options to use for assembler.
>  
>  AFLAGS_KERNEL
>  --------------------------------------------------
> -Additional options for $(AS) when used for assembler
> -code for code that is compiled as built-in.
> +Additional options when used for assembling code that is compiled as built-in.
>  
>  KCFLAGS
>  --------------------------------------------------
> diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
> index d65ad5746f94..f0b3a30b985d 100644
> --- a/Documentation/kbuild/makefiles.txt
> +++ b/Documentation/kbuild/makefiles.txt
> @@ -306,7 +306,7 @@ more details, with real examples.
>  	variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
>  	entire tree.
>  
> -	asflags-y specifies options for assembling with $(AS).
> +	asflags-y specifies options for assembling.
>  
>  	Example:
>  		#arch/sparc/kernel/Makefile
> @@ -441,7 +441,7 @@ more details, with real examples.
>  	as-instr checks if the assembler reports a specific instruction
>  	and then outputs either option1 or option2
>  	C escapes are supported in the test instruction
> -	Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
> +	Note: as-instr-option uses KBUILD_AFLAGS for assembler options
>  
>      cc-option
>  	cc-option is used to check if $(CC) supports a given option, and if
> @@ -814,7 +814,7 @@ When kbuild executes, the following steps are followed (roughly):
>  	In this example, the binary $(obj)/image is a binary version of
>  	vmlinux. The usage of $(call if_changed,xxx) will be described later.
>  
> -    KBUILD_AFLAGS		$(AS) assembler flags
> +    KBUILD_AFLAGS		assembler flags
>  
>  	Default value - see top level Makefile
>  	Append or modify as required per architecture.
> @@ -853,15 +853,15 @@ When kbuild executes, the following steps are followed (roughly):
>  	The first example utilises the trick that a config option expands
>  	to 'y' when selected.
>  
> -    KBUILD_AFLAGS_KERNEL	$(AS) options specific for built-in
> +    KBUILD_AFLAGS_KERNEL	assembler options specific for built-in
>  
>  	$(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile
>  	resident kernel code.
>  
> -    KBUILD_AFLAGS_MODULE   Options for $(AS) when building modules
> +    KBUILD_AFLAGS_MODULE   Options for assembler when building modules
>  
>  	$(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that
> -	are used for $(AS).
> +	are used for assembler.
>  	From commandline AFLAGS_MODULE shall be used (see kbuild.txt).
>  
>      KBUILD_CFLAGS_KERNEL	$(CC) options specific for built-in
> -- 
> 2.17.1
>