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Date: Tue, 16 Sep 2008 10:53:05 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Yinghai Lu <yhlu.kernel@gmail.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       jbaron <jbaron@redhat.com>
Subject: Re: [PATCH] introduce boot_printk()
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Yinghai Lu wrote:
> 
> it seem using pci_printk or acpi_printk.. could be more flexible.
> 
> otherwise will need to keep update linux/kernel.h to add so call subsys tags...
> 
> use only need to
> have DEFINE_LOGLEVEL_SETUP(xxx) in c
> and have DECLARE_LOGLEVEL(xxx) in .h
> then just use xxx_printk
> 

Uh?  You can add the subsys tags elsewhere if you prefer too.

However, there are a few important differences to keep in mind.  Tags 
get logged in the dmesg buffer even if not printed to the kernel, 
whereas a jump-based architecture will not just suppress the output, but 
even the formatting of the output.  Either is a good thing for certain 
things, and a bad thing for other things.

I personally think the kind of things discussed belong in the category 
of "always put in the dmesg buffer", and like the idea of 
subsystem-tagging them.

	-hpa