linux-kernel - Re: early_printk accessing __log

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Message-Id: <200707182337.34767.rgetz@blackfin.uclinux.org>
Date:	Wed, 18 Jul 2007 23:37:34 -0400
From:	Robin Getz <rgetz@...ckfin.uclinux.org>
To:	"Mike Frysinger" <vapier.adi@...il.com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: early_printk accessing __log_buf

On Wed 18 Jul 2007 19:53, Mike Frysinger pondered:
> On 7/18/07, Robin Getz <rgetz@...ckfin.uclinux.org> wrote:
> > On Wed 18 Jul 2007 18:16, Andrew Morton pondered:
> > > I'd suggest that any interface into here should be via function calls,
> > > not via direct access to printk internals: think up some nice
> > > copy_me_some_of_the_log_buffer() interface.
> >
> > If so - I would still like to put it in:
> >  - ifdef CONFIG_EARLY_PRINTK
> >  - and define as __init
> >
> > so that people don't use it when they shouldn't (when the kernel is up an
> > running).
> >
> > Something simple like - early_copy_log_buff(void *dest, size_t n)
> >
> > copies n bytes from log_buf to memory area dest. Returns number of bytes that
> > could not be copied. Can find out how many bytes are in the log_buff by
> > calling with zero size.
> >
> > This is not destructive to existing interfaces (log_start and con_start are
> > not updated/used). This should ensure that if booting does work - that normal
> > messages come out the standard method.
> >
> > Any other suggestions?
> 
> maybe something as cheesy as early_get_log_buf() ?  that way you dont
> have to do any buffer management, you can just operate read-only on
> the string ...

I actually thought I might just do something like:

  char *c;
  while (early_copy_log_buff(c, 1))
	out_early_serial_byte(c);

that way - I don't need to be very complex in the arch code.

That is about as cheesy/easy as I could think of...

-Robin
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