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

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Message-ID: <20140328205836.GN25519@cbox>
Date:	Fri, 28 Mar 2014 13:58:36 -0700
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Rob Herring <robherring2@...il.com>
Cc:	Olof Johansson <olof@...om.net>,
	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.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 02:19:23PM -0500, Rob Herring wrote:
> 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.
> 
In Ubuntu, recent versions at least, it's all just hardcoded in
/etc/init/*.conf files.  The Linaro OE FS does check /proc/cmdline for
console= in there - not sure if we care, or at least we can have it
fixed quickly.

-Christoffer
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