linux-kernel - Re: [PATCH v4 0/4] Add support for DEVNAME:0.0 style hardware based addressing

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Date: Mon, 18 Dec 2023 08:38:37 +0200
From: Tony Lindgren <tony@...mide.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, Petr Mladek <pmladek@...e.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: "David S . Miller" <davem@...emloft.net>,
	Andy Shevchenko <andriy.shevchenko@...el.com>,
	Dhruva Gole <d-gole@...com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Johan Hovold <johan@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Vignesh Raghavendra <vigneshr@...com>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v4 0/4] Add support for DEVNAME:0.0 style hardware based
 addressing

* Tony Lindgren <tony@...mide.com> [231208 10:29]:
> * Tony Lindgren <tony@...mide.com> [700101 02:00]:
> > * Tony Lindgren <tony@...mide.com> [700101 02:00]:
> > > We also prepare the serial core to handle the ttyS related quirks done
> > > in console_setup() to prepare things for eventually dropping the parsing
> > > from console_setup(). This can only happen after further changes to
> > > register_console().
> > 
> > Petr FYI, so for dropping the console_setup() parsing, below is a hack
> > patch to see what goes wrong in register_console() if you have some ideas
> > on how to handle this.
> > 
> > We end up with the console device backed up seria8250 instead of ttyS0,
> > and earlycon won't get properly disabled. And of course other consoles
> > beyond ttyS need to be also considered.
> 
> Hmm so the following extra patch seems to fix the issues based on light
> testing. But is it safe to assume that if CON_PRINTBUFFER is set we can
> disable the bootconsole?

OK so no need for the CON_PRINTBUFFER change, it's wrong. I found a few
bugs causing this issue and a lot of other confusion while testing:

- In console_setup(), a DEVNAME:0.0 style console can get added with the
  IO address turned into a ttyS console with some crazy index :) So we
  need to bail out early on consoles with ':' in the name.

- The brl_opts can be empty or NULL, but we need to pass NULL to
  __add_preferred_console() to get CON_CONSDEV flag set for DEVNAME:0.0
  console. Otherwise the preferred_console won't get set and the boot
  console won't get disabled.

- The console_set_on_cmdline flag needs to be set if console_setup()
  does not call __add_preferred_console() for DEVNAME:0.0 style console
  as otherwise try_enable_default_console() may get called before the
  console handling driver has added the preferred console.

I think with these the remaining issues are sorted out :) I'll post a
v5 set with as RFC as it's getting close to the merge window.

Regards,

Tony