[Buildroot] [PATCH] systemd: let getty instead of serial-getty handle /dev/console

From: Peter Seiderer <ps.report@gmx.net>
To: buildroot@busybox.net
Subject: [Buildroot] [PATCH] systemd: let getty instead of serial-getty handle /dev/console
Date: Thu, 22 Sep 2016 20:50:12 +0200	[thread overview]
Message-ID: <20160922205012.13722beb@gmx.net> (raw)
In-Reply-To: <68b49446-0228-174d-ad47-9209d23ae90a@je-eigen-domein.nl>

Hello Floris,

On Wed, 21 Sep 2016 23:47:02 +0200, Floris Bos <bos@je-eigen-domein.nl> wrote:

> On 09/21/2016 10:05 PM, Peter Seiderer wrote:
> > Hello *,
> >
> > On Wed, 21 Sep 2016 09:01:37 +0200, Peter Korsgaard <peter@korsgaard.com> wrote:
> >
> >>>>>>> "Yann" == Yann E MORIN <yann.morin.1998@free.fr> writes:
> >>   > Floris, All,
> >>   > On 2016-09-09 18:10 +0200, Floris Bos spake thusly:
> >>   >> The serial-getty unit depends on dev-%i.device which does not
> >>   >> seem to be created for /dev/console
> >>   >> Workaround this by letting normal getty unit handle things
> >>   >> if BR2_TARGET_GENERIC_GETTY_PORT is set to 'console'
> >>   >>
> >>   >> Signed-off-by: Floris Bos <bos@je-eigen-domein.nl>
> >>
> >>   > I haven't tested that, but I think this is OK just on principle.
> >>
> >>   > I just wonder if that behaves correctly when console is a serial line or
> >>   > anything else (e.g. a VT on HDMI, or through a debug channel...)
> >>
> >> Yeah, me too. Does anybody know what the difference exactly is between
> >> getty/serial-getty, and when one should be used over the other?
> >>
> > Tested for the rpi3/glibc/systemd case and failed: I get a doubled
> > (and unusable) ' Welcome to Buildroot/buildroot login:' on serial and
> > no login on hdmi...
> 
> Empty cmdline.txt will give hdmi.
> 
> Recall you need "console=serial0,115200 console=tty1" with tty1 last in 
> cmdline.txt if you want them simultaneous.

Changed cmdline.txt to:

	root=/dev/mmcblk0p2 rootwait console=ttyAMA0,115200 console=tty1

Which gives me two (functional) logins on serial and hdmi.

But I think changing package/rpi-firmware/cmdline.txt unconditional will
break the other Init systems, see commit log from last patch touching
cmdline.txt ([1):

  ...change BR2_TARGET_GENERIC_GETTY_PORT to "console", so it starts a
  getty on the last console= passed to the kernel, ttyAMA0...

Regards,
Peter

[1] https://git.buildroot.net/buildroot/commit/?id=20878a1017e2bf7eb8c5f870dc6d2641493cb0f9

> So that tty1 becomes /dev/console and serial is handled by systemd's 
> automatic getty generator.
> 
> Perhaps there is an issue if you have the order swapped, and both 
> systemd's automatic stuff and the manual symlink try to display a getty 
> on serial.
> Not sure how to disable systemd's automatic behavior.
> 
> 
> 
> Yours sincerely,
> 
> Floris Bos
> 
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