linux-kernel - [PATCH 0/8] printk: Clean up preferred console handling

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Message-ID: <20260206165002.496724-1-pmladek@suse.com>
Date: Fri,  6 Feb 2026 17:49:54 +0100
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Chris Down <chris@...isdown.name>,
	linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>
Subject: [PATCH 0/8] printk: Clean up preferred console handling

Hi,

this patches does some clean up of the code for handling preferred consoles
in the console registration code.

  + 1st and 2nd patch try to improve a naming.

    The meaning of struct console_cmdline has changed over time.
    The meaning of "preferred_console" variable has always been a bit
    confusing and it has got even worse after adding the support for
    Braille consoles.


  + 3rd patch remove some code duplication. It better defines and describes
    the rules for adding and updating preferred consoles. It uses a more
    defensive coding style.


  + 4th, 5th, and 6th patch improve handling of Braille consoles.
    They are preferred via the command line but they do not get
    printk() messages and are not associated with /dev/console.

    The new code makes this more obvious. Also it explicitly
    defines the relation against default consoles and other
    non-Braille preferred consoles.


  + 7th patch removes a hidden side effect of
    try_enable_preferred_console()


  + 8th patch removes the last hidden side effect of
    try_enable_preferred_console() and allows to call it
    only when there are any non-Braille preferred consoles.


I tested many scenarios of fixed several bugs. I did my best to
prevent regressions.

This patchset is a prerequisite for Marcos' clean up of CON_ENABLE
flag handling. It should prevent regressions caused by the
hidden effects of try_enable_preferred_console(), for example,
see https://lore.kernel.org/r/89409a0f48e6998ff6dd2245691b9954f0e1e435.camel@suse.com

Also I am working on a feature which would allow to explicitly
enable/prefer consoles proposed by SPCR, device tree, or
platform-specific code using a generic "console=platform".
This clean up is a prerequisite, see
https://github.com/pmladek/linux/tree/console-platform-poc1-iter9

The patchset has been re-based on top of v6.19-rc8.

Petr Mladek (8):
  printk: Rename struct console_cmdline to preferred_console
  printk: Rename preferred_console to preferred_dev_console
  printk: Separate code for adding/updating preferred console metadata
  printk: Cleanup _braille_(un)register_console() wrappers
  printk: Try to register each console as Braille first
  printk: Do not set Braille console as preferred_console
  printk: Handle pre-enabled consoles directly in register_console()
  printk: Try enable preferred consoles only when there are any

 .../accessibility/braille/braille_console.c   |   7 +-
 kernel/printk/braille.c                       |  20 +-
 kernel/printk/braille.h                       |  23 +-
 .../{console_cmdline.h => console_register.h} |   6 +-
 kernel/printk/printk.c                        | 295 ++++++++++++------
 5 files changed, 223 insertions(+), 128 deletions(-)
 rename kernel/printk/{console_cmdline.h => console_register.h} (83%)

-- 
2.52.0