linux-kernel - Re: earlycon: no match?

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Message-ID: <20150504202223.GT6325@pengutronix.de>
Date:	Mon, 4 May 2015 22:22:23 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Robert Schwebel <r.schwebel@...gutronix.de>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: earlycon: no match?

On Mon, May 04, 2015 at 10:01:37AM -0400, Peter Hurley wrote:
> Hi Robert,
> 
> On 05/03/2015 05:10 PM, Robert Schwebel wrote:
> > Hi Peter,
> > 
> > with 4.1-rc1, my boxes with early console enabled show something like
> > this (the example is vexpress, but it for example also happens on an
> > AM335x board):
> > 
> >   earlycon: no match for ttyAMA0,38400n8
> 
> This shouldn't impact any previous earlycon setup. Are you saying
> you're seeing a regression?
> 
> How do you have early console enabled, via the command line or via DT?

What happens here is that Robert has console=ttyAMA0,38400n8 in his
command line. In init/main.c we have:

static int __init do_early_param(char *param, char *val, const char *unused)
{
	const struct obs_kernel_param *p;

	for (p = __setup_start; p < __setup_end; p++) {
		if ((p->early && parameq(param, p->str)) ||
		    (strcmp(param, "console") == 0 &&
		     strcmp(p->str, "earlycon") == 0)
		) {
			if (p->setup_func(val) != 0)
				pr_warn("Malformed early option '%s'\n", param);
		}
	}
	/* We accept everything at this stage. */
	return 0;
}

This means that param_setup_earlycon() gets called with the arguments
passed to the console= parameter which makes no sense in this context
and leads to the "no match for" message.

Sascha

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