linux-kernel - Re: [RFC 0/5] of: Automatic console registration cleanups

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Message-ID: <CAL_JsqKFO+OSz83f=XdyKgCqByUvHe7qLzgn5QLU1x1V1A5Fng@mail.gmail.com>
Date:	Fri, 28 Mar 2014 14:19:23 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Olof Johansson <olof@...om.net>
Cc:	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Rob Herring <rob.herring@...aro.org>
Subject: Re: [RFC 0/5] of: Automatic console registration cleanups

On Fri, Mar 28, 2014 at 1:56 PM, Olof Johansson <olof@...om.net> wrote:
> On Fri, Mar 28, 2014 at 09:08:00AM -0700, Grant Likely wrote:
>> Hi all,
>>
>> This is a series that I've been playing with over the last few days to
>> clean up the selection of default console devices when using the device
>> tree. The device tree defines a way of specifying the console by using a
>> "stdout-path" property in the /chosen node, but very few drivers
>> actually attempt to use that data, and so for most platforms there needs
>> to be a "console=" line in the command line if a serial port is intended
>> to be used as the console.
>>
>> With this series, if there is a /chosen/stdout-path property, and if
>> that property points to a serial port node, then when the serial driver
>> registers the port, the core uart_add_one_port() function will notice
>> and if no console= argument was provided then add it as a preferred
>> console.
>>
>> I've not tested this very extensively yet, but I want to get some
>> feedback before I go further.
>>
>> The one downside with this approach is that it doesn't do anything for
>> early console setup. That still needs to be added on a per-driver basis,
>> but at least it shouldn't conflict with this approach.

I'm working on the early aspect. I've got things working with either
command line (which I sent out recently) and with parsing the FDT
(which I haven't sent out yet).

> Looks sane to me (as discussed in person). I gave it a run on PWRficient with
> and without console= line (8250-based uart), and it behaved as expected.
>
> A couple of nits on the series, replied to two of the patches.
>
> I'll give it a run through the board farm here too, but I'll keep console=
> bootargs there for those boots at this time, too much to change to take it out
> everywhere. :-)

It would be good to know if removing console= causes userspace any
issues. For example, if getty's were setup based on console params. I
know ubuntu does some detection of serial ports, but I don't recall
what it looks at. Hopefully it's just checking /dev nodes.

Rob
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