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Re: [PATCH] kill prom_printf

To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Subject: Re: [PATCH] kill prom_printf
From: Juan Quintela <quintela@trasno.org>
Date: Tue, 17 Jun 2003 17:03:24 +0200
Cc: Ladislav Michl <ladis@linux-mips.org>, linux-mips@linux-mips.org
In-reply-to: <Pine.GSO.3.96.1030617154243.22214F-100000@delta.ds2.pg.gda.pl> (Maciej W. Rozycki's message of "Tue, 17 Jun 2003 15:44:32 +0200 (MET DST)")
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References: <Pine.GSO.3.96.1030617154243.22214F-100000@delta.ds2.pg.gda.pl>
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>>>>> "maciej" == Maciej W Rozycki <macro@ds2.pg.gda.pl> writes:

maciej> On Tue, 17 Jun 2003, Juan Quintela wrote:
maciej> So you need to explicitly configure it?  That's very bad.
>> 
>> You bet:
>> - you force everybody to use early_printk (you only want it for
>> debugging).
>> - you configure early_printk for everybody (never have to configure
>> it).
>> 
>> You can't have the cake and eat it :(

maciej> I'm not sure what you mean.  Please elaborate.

As it is used in the other platforms:

- you setup your console (there is a console by default).
- until that console is initilized, messages are buffered.

that is clearly bad if your system stops before initializing the
console: i.e. zero output.

- early_printk to the rescue, as soon as you can print, you initialize
  the console, and begin printing.

- so far so god.

- now it is time to initialize the real console (reading
  console=<blah> ....)
- output from now one goes to the real console.

Problems:
a - you want all your messages in your console, and your console is not
  the console used by early_printk.  Some meassages dissapear, why?
  because early_printk is the default -> you don't want early_printk
  by default.uu

b - you want at least some output if the kernel hangs early -> you want
  early_printk by default.

I am not able to make happy people in the a) group or people in the b)
group, but not both at the same time with the default early_console.


I hope that now explanation is better (for sure that it is larger).

>> Why do you ever will want not to use early_printk?

maciej> I won't, but someone else certainly will.

I meaned here somebody in general, not you in particular :p

Later, Juan.

-- 
In theory, practice and theory are the same, but in practice they 
are different -- Larry McVoy

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