linux-kernel - [patch] Fixes and cleanups for earlyprintk aka boot console.

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Date:	Tue, 20 Feb 2007 12:35:49 +0100
From:	Gerd Hoffmann <kraxel@...e.de>
To:	linux kernel mailing list <linux-kernel@...r.kernel.org>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [patch] Fixes and cleanups for earlyprintk aka boot console.

  Hi,

The console subsystem already has an idea of a boot console, using the
CON_BOOT flag.  The implementation has some flaws though.  The major
problem is that presence of a boot console makes register_console()
ignore any other console devices (unless explicitly specified on the
kernel command line).

This patch fixes the console selection code to *not* consider a boot
console a full-featured one, so the first non-boot console registering
will become the default console instead.  This way the unregister call
for the boot console in the register_console() function actually
triggers and the handover from the boot console to the real console
device works smoothly.  Added a printk for the handover, so you know
which console device the output goes to when the boot console stops
printing messages.

The disable_early_printk() call is obsolete with that patch, explicitly
disabling the early console isn't needed any more as it works
automagically with that patch.

I've walked through the tree, dropped all disable_early_printk()
instances found below arch/ and tagged the consoles with CON_BOOT if
needed.

The code is tested on x86 only so far.  It is probably a good idea to
run it in -mm for a while to shake out any architecture issues which
might show up.  Comments?

cheers,

  Gerd

-- 
Gerd Hoffmann <kraxel@...e.de>

View attachment "early-printk-boot-console.patch" of type "text/x-patch" (10597 bytes)