linux-kernel - Re: Early printk behaviour

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Date:	Fri, 17 Aug 2007 17:09:39 -0400
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Robin Getz" <rgetz@...ckfin.uclinux.org>
Cc:	"Gerd Hoffmann" <kraxel@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: Early printk behaviour

On 8/17/07, Robin Getz <rgetz@...ckfin.uclinux.org> wrote:
> On Fri 17 Aug 2007 03:49, Gerd Hoffmann pondered:
> > Mike Frysinger wrote:
> > >> Hmm, sort of, although I didn't think about the case of no real console
> > >> replacing the early console.  The intention of the patch is to have a
> > >> smooth handover from the boot console to the real console.  And, yes, if
> > >> no real console is ever registered the boot console keeps running ...
> > >
> > > i think it also occurs in the case where real console != early console
> >
> > No.  At least not of the boot console has the CON_BOOT flag set as it
> > should.  Last message you'll see on the boot console is the handover
> > printk, telling you which real console device prints the following
> > messages.  Whenever early and real console go to the physical device or
> > not doesn't matter.
> >
> > >> So you can either let it running and *not* mark it __init, so it can
> > >> keep on going without breaking.  Or you can explicitly unregister your
> > >> boot console at some point, maybe using a late_initcall.
> > >
> > > wouldnt a common kernel late_initcall() be more appropriate ?  if
> > > early console hasnt switched over (for whatever reason), then kill it
> >
> > Hmm, yes, should be doable in generic code.  Check whenever the current
> > console has CON_BOOT set and if so unregister it.
>
> Something like:
>
> Index: kernel/printk.c
> ===================================================================
> --- kernel/printk.c     (revision 3568)
> +++ kernel/printk.c     (working copy)
> @@ -1104,6 +1104,22 @@
>  }
>  EXPORT_SYMBOL(unregister_console);
>
> +int __init disable_boot_consoles(void)
> +{
> +       struct console *con;
> +
> +       for (con = console_drivers; con; con = con->next) {
> +               if (con->flags & CON_BOOT) {
> +                       printk(KERN_INFO "Unregister BootConsole %s%d\n",
> +                               con->name, con->index);
> +                       unregister_console(con);
> +               }
> +       }
> +       return 0;
> +}
> +late_initcall(disable_boot_consoles);

is there any need for a return value then ?
void __init disable_boot_consoles(void);

and if we dont think anyone else wants to call it ...
static void __init disable_boot_consoles(void);
-mike
-
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