linux-kernel - Re: [PATCH v3 -next 11/11] serial: 8250_early: Remove setup_early_serial8250

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Date:	Fri, 3 Apr 2015 17:52:58 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.cz>, Rob Herring <robh@...nel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v3 -next 11/11] serial: 8250_early: Remove setup_early_serial8250_console()

On Fri, Apr 3, 2015 at 11:27 AM, Peter Hurley <peter@...leysoftware.com> wrote:
> On 04/03/2015 01:44 PM, Yinghai Lu wrote:
>> On Fri, Apr 3, 2015 at 10:38 AM, Peter Hurley <peter@...leysoftware.com> wrote:
>>> On 04/03/2015 12:57 PM, Yinghai Lu wrote:
>>>
>>> Wait -- you have earlycon in a product??
>>
>> What do you mean?
>
> I mean, what will happen if I put in a big debug banner like Steven
> did for ftrace?
>
> Kernel developers need earlycon for debugging arch code; often the earlycon
> is just hacked together especially when it requires fixmap support.
>
> Putting it in a product and _relying on undocumented behavior_ is a bad idea.

let me repeat again:
when you have "console=uart8250,io,0x3f8", you will have earlycon and
then console.

That is just for kernel developer for debugging.

When you have x86 with bunch of dimms and cpus, user will have to wait couple
of minutes to output from console=ttyS0....and if it hang early, no
one would know what happen.

Also it is only boot time only....
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