From: Andi Kleen <ak@muc.de>
To: Andrew Morton <akpm@digeo.com>
Cc: James Simmons <jsimmons@infradead.org>,
Anton Blanchard <anton@samba.org>,
" " "Martin J. Bligh" <mbligh@aracnet.com>,
linux-kernel@vger.kernel.org, " "@averellmail.firstfloor.org,
torvalds@transmeta.com,
" " Linux console project
<linuxconsole-dev@lists.sourceforge.net>
Subject: Re: [BK PATCH] console changes 1
Date: 14 Oct 2002 03:18:12 +0200 [thread overview]
Message-ID: <m3adlhkecr.fsf@averell.firstfloor.org> (raw)
In-Reply-To: <3DA9E439.3613F889@digeo.com>
Andrew Morton <akpm@digeo.com> writes:
> I think what we need James is just the low-level hook in printk.c which
> the various platforms and boards can plug into. The one in Martin's
> patch (module some cleanups, docco, conversion to C, etc) looks
> suitable to me. The actual early console drivers don't appear to have
> much relationship at all to the console layer really. They're just
> minimal-code busy-wait port banging.
The hook already exists and it is called register_console. Has been there
for years. early_printk on x86-64 uses that. Originally I used the hackish
printk hook way, but Linus put me on the right track.
Your arch code just does a register_console very early which does the low level
output.
Actually you need one new hook for cosmetic reason: when the real console
starts you want to disable the early console, otherwise you get duplicated
output when they go to the same output device. This can be done with a
straight forward function call in console_init.
BTW the x86-64 early console should just work fine on i386 too, with minor
changes.
All you need to do is:
- cp arch/x86_64/kernel/early_printk.c arch/i386/kernel/early_printk.c
- edit arch/i386/kernel/early_printk.c and replace VGABASE with
__PAGE_OFFSET+0xb8000
- add it to arch/i386/kernel/Makefile
- (optional - if you don't do it will be only initialised after setup_arch when
__setup arguments are parsed)
add something like
if (c == ' ' && !memcmp(from,"earlyprintk=",12)) {
extern int setup_early_printk(char *opt)
setup_early_printk(from+12);
}
to the comand line parsing in arch/i386/kernel/setup.c
- Enable CONFIG_EARLY_PRINTK so that console_init disables it.
- Boot with earlyprintk=vga (for vga output)
or earlyprintk=serial,ttySx,baud for serial output.
Add ,keep when you want to keep it even after console_init
-Andi
next prev parent reply other threads:[~2002-10-14 1:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-12 1:06 [BK PATCH] console changes 1 James Simmons
2002-10-12 1:29 ` Martin J. Bligh
2002-10-12 1:40 ` James Simmons
2002-10-12 1:43 ` Anton Blanchard
2002-10-12 2:24 ` Martin J. Bligh
2002-10-13 20:40 ` James Simmons
2002-10-13 20:49 ` Martin J. Bligh
2002-10-13 21:00 ` Russell King
2002-10-13 21:23 ` Andrew Morton
2002-10-14 1:18 ` Andi Kleen [this message]
2002-10-13 22:31 ` Anton Blanchard
2002-10-12 19:22 ` Dave Hansen
2002-10-12 19:23 ` William Lee Irwin III
2002-10-12 23:43 ` Anton Blanchard
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