Date: Fri, 2 Jan 2009 18:50:23 +0900
From: Paul Mundt <lethal@linux-sh.org>
To: Rob Landley <rob@landley.net>
Cc: Embedded Linux mailing list <linux-embedded@vger.kernel.org>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       "H. Peter Anvin" <hpa@zytor.com>, Sam Ravnborg <sam@ravnborg.org>
Subject: Re: PATCH [0/3]: Simplify the kernel build by removing perl.
Message-ID: <20090102095023.GA28078@linux-sh.org>
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	Rob Landley <rob@landley.net>,
	Embedded Linux mailing list <linux-embedded@vger.kernel.org>,
	linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Sam Ravnborg <sam@ravnborg.org>
References: <200901020207.30359.rob@landley.net>
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On Fri, Jan 02, 2009 at 02:07:28AM -0600, Rob Landley wrote:
> Before 2.6.25 (specifically git bdc807871d58285737d50dc6163d0feb72cb0dc2 ) 
> building a Linux kernel never required perl to be installed on the build 
> system.  (Various development and debugging scripts were written in perl and 
> python and such, but they weren't involved in actually building a kernel.)  
> Building a kernel before 2.6.25 could be done with a minimal system built from 
> gcc, binutils, bash, make, busybox, uClibc, and the Linux kernel, and nothing 
> else.  (Embedded developers creating clean cross compile environments that 
> won't leak bits of the host system into the target, or bootstrapping native 
> development environments to run on target hardware or under emulators, tend to 
> care about this sort of thing.)
> 
> The perl checkin for 2.6.25 was the camel's nose under the tent flap, and 
> since then two more instances of perl have shown up in the core kernel build.  
> This patch series removes the three required to build a basic kernel for qemu 
> for the targets I've tested (arm, mips, powerpc, sparc, m68k, sh4, and of 
> course x86 and x86-64), replacing them with shell scripts.

Misguided rhetoric aside, what does this actually accomplish? If folks
add meaningful tools in to the kernel that require python, and it is
generally regarded as being fairly ubiquitous, I can't imagine there
being any substantiated objections against it.

Your main reasons against inclusion of perl seem to be that there is no
realistic expectation for target systems that will be self-hosting will
have perl included, or the inherent complexity in maintaining a coherent
cross compiling environment. Both of these things are issues with your
own environment, and in no way are these representative of the embedded
development community at large.

Now with that out of the way, this entire series fundamentally fails to
convert half of the perl scripts shipped with the kernel today, some that
are required for build depending on Kconfig options, and others that are
simply useful tools for self-hosted environments. Simply converting a
couple of scripts over you find objectionable is certainly fine if there
is a real benefit in doing so, but this doesn't actually accomplish your
goal of removing the perl dependency.

Ignoring the compile-time dependencies that you overlooked, what you
define as "development and debugging" scripts are still an integral part
of the system, unless you are trying to argue that embedded developers
have no interest in things like checkstack due to the trouble of trying
to get perl built.

Until you can post a series that converts all of scripts/*.pl in its
entirety, you have failed to address the fundamental reason why perl is
used in the first place. Trying to toss bizarre policy statements around
regarding things you personally find objectionable without any coherent
technical argument to the contrary is of no constructive use whatsoever.

The kernel is and always has been about using the right tool for the job,
not a matter of dictating what tools you must use in order to accomplish
a task you are interested in. Common sense does apply here though, so
this might be a more daunting task for some than others.
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