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Date: Wed, 06 Aug 2008 16:02:54 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Matt Mackall <mpm@selenic.com>
CC: Tim Bird <tim.bird@am.sony.com>,
       Robert Schwebel <r.schwebel@pengutronix.de>,
       linux kernel <linux-kernel@vger.kernel.org>,
       linux-embedded <linux-embedded@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] bootup: Add built-in kernel command line for x86
References: <489A1844.3090502@am.sony.com>	 <20080806220445.GB10168@pengutronix.de> <489A2419.2030900@am.sony.com>	 <489A2A24.6010400@zytor.com> <1218063133.7576.16.camel@calx>
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Matt Mackall wrote:
> On Wed, 2008-08-06 at 15:48 -0700, H. Peter Anvin wrote:
>> Tim Bird wrote:
>>> One difficulty is that the other arches' command lines
>>> are not currently "broken", so there's no real incentive
>>> to change them.
>>>
>>> The only thing novel thing I'm adding here is the addition of
>>> the leading '!' to allow for an override.  This is needed
>>> in some x86 cases I'm familiar with, but I've haven't seen
>>> any cases where it would be useful for other arches.
>>> (not to say they don't exist - I just haven't seen them.)
>>>
>> Note that it could just as easily be done with a CONFIG_CMDLINE_OVERRIDE 
>> option, since the initial reason for a magic character was to be able to 
>> provide both prefix and suffix splicing.
> 
> You're right, I had forgotten about the suffix splicing and my brain is
> a bit foggy on what motivated it.
> 

Well, prefix = bootloader overrides; suffix = builtin overrides.

>> CONFIG_CMDLINE_OVERRIDE is probably more palatable to other architectures.
> 
> Yes, though I doubt we're in danger of introducing any real backwards
> compatibility issues with the magic '!' at the beginning.

Well, it does if we want to make this a generic feature, which I believe 
we should.

	-hpa