linux-kernel - Re: [PATCH v4 0/4] Fixes for console command line ordering

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Date: Fri, 21 Jun 2024 16:44:10 +0200
From: Petr Mladek <pmladek@...e.com>
To: Tony Lindgren <tony.lindgren@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Torvalds <torvalds@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Tony Lindgren <tony@...mide.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/4] Fixes for console command line ordering

Added Linus into Cc.

On Thu 2024-06-20 15:45:25, Tony Lindgren wrote:
> Hi,
> 
> Recent changes to add support for DEVNAME:0.0 style consoles caused a
> regression with the preferred console order where the last console on
> the kernel command line is no longer the preferred console.
> 
> The following four changes fix the issue using Petr's suggestion that
> does not involve calling __add_preferred_console() later on again, and
> adds the deferred consoles to the console_cmdline[] directly to be
> updated when the console is ready.
> 
> We revert the earlier printk related changes, and then add back the
> DEVNAME:0.0 functionality based on Petr's code snippet. And we end up
> reducing the code quite a bit too this way.
> 
> And we also revert all the unusable serial core console quirk handling,
> it does not do anything for the legacy "ttyS" named consoles. And then
> we add a minimal serial_base_match_and_update_preferred_console().
> 
> The reason we want DEVNAME:0.0 style consoles is it helps addressing the
> console based on the connected serial port controller device rather than
> using the hardcoded ttyS addressing. And that helps with issues related
> to the console moving around after togging the HSUART option in the BIOS,
> or when new ports are enabled in devicetree and aliases are not updated.
> 
> Tony Lindgren (4):
>   printk: Revert add_preferred_console_match() related commits
>   printk: Add match_devname_and_update_preferred_console()
>   serial: core: Revert unusable console quirk handling
>   serial: core: Add serial_base_match_and_update_preferred_console()
> 
>  drivers/tty/serial/8250/8250_core.c  |   5 -
>  drivers/tty/serial/serial_base.h     |  22 +---
>  drivers/tty/serial/serial_base_bus.c | 116 +++------------------
>  drivers/tty/serial/serial_core.c     |   2 +-
>  include/linux/printk.h               |   5 +-
>  kernel/printk/Makefile               |   2 +-
>  kernel/printk/conopt.c               | 146 ---------------------------
>  kernel/printk/console_cmdline.h      |   7 +-
>  kernel/printk/printk.c               | 122 ++++++++++++++++------
>  9 files changed, 112 insertions(+), 315 deletions(-)
>  delete mode 100644 kernel/printk/conopt.c

The patchset looks ready for linux-next. And I have pushed it
into printk/linux.git, branch for-6.10-register-console-devname.

I am not sure about the mainline. We need to fix the regression in 6.10.
The change is not trivial and rc5 is knocking on the doors.

Unfortunately, the patchset intermixes reverts and new code.
So that it can't be used for simple revert as is.

I am quite confident that the new code works as expected.
It changes tricky code but the logic of the change is quite
straightforward.


I see three solutions:

1. Linus could merge the changes directly into rc5.

2. I could send a pull request after it survives few days in
   linux-next.

3. Or we rework the patchset. And do pure revert for 6.10 and
   add the feature a clean way for-6.11.


I personally prefer the 3rd solution. But I am super conservative.
I guess that most other people would go with the other 2 solutions.

Best Regards,
Petr