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Fri, 06 Nov 2026 09:20:18 -0800 (PST) Received: from pathway.suse.cz ([176.114.240.130]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49354fc5ab4sm2701646f8f.30.2026.11.06.09.20.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2026 09:20:17 -0800 (PST) From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Steven Rostedt , Marcos Paulo de Souza , Chris Down , Naveen Kumar Chaudhary , printk@lists.linux.dev, linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH v6 00/16] printk: Clean up preferred console handling Date: Fri, 6 Nov 2026 18:19:36 +0100 Message-ID: <20261106171952.207909-1-pmladek@suse.com> X-Mailer: git-send-email 2.56.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi, this patchset does some clean up of the code for handling preferred consoles in the console registration code. It is a prerequisite some more patchsets, namely: + 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 + for Chris' per-console log-level, see https://lore.kernel.org/r/cover.1764272407.git.chris@chrisdown.name and maybe even some more. Changes against [v5]: + Updated comment about preferred_consoles[] (1st patch) [Chris] + Removed extra newline (1st patch) [Chris] + Added back two comments (4th patch) [John] + Fixed kernel-doc formatting (4th patch) [Chris] + Added check for empty @name or @devname (5th patch (new)) [Chris] + Fixed typos (6th patch) [Chris] + Added back "[*]" (7th patch) [John] + Removed problematic patch which allowed to override console options via the command line (9th patch in v5)) [Chris] + Added comment about that console_call_setup() was made global only for Braille console driver. (11th patch) [Chris] + Reworked description of behavior changes when preferring Braille over non-Braille preferred console entries (13th patch) [Chris] + Fixed comment: s/preferred_console/preferred_dev_console/ (13th patch) [Chris] + Optimize handling of preferred_dev_console list (14th patch) [Chris] + Added Reviewed-by and Acked-by tags. Changes against [v4]: + Removed 1st patch from v4. Already in upstream. + Cleanup _braille_(un)register_console() wrappers already in 3rd patch. is_braille_console_preferred() will be needed sooner. + Split 4th patch. Start with reshufling the add_preferred_console() code without any functional changes. Add the various checks and behavior changes one by one is a followup patches. + Rework the code to make it clear when it is a new entry or an update. + Put back braille_set_options() which just updates the optional entry. The logic when the value should get updated is the same as for pc->options. + Make sure that options can be overridden by the command line. + Add preferred_dev_node to remember the ordering of preferred consoles. Use it when the last one becomes Braille. The previous version tried to remembered just the last preferred console. But the logic because pretty complicated when I tried to make it error proof. AI was able to find many scenarios where it broke. The list is the ultimate solution and is easier in the end. + Use console_call_setup() in braille_register_console() instead of duplicating the code [John] Changes against [v3]: + Move the handling of pre-enabled consoles into register_console() as 1st patch. It prevents a possible invalid access. [Petr] + Move the code for handling pre-enabled to console to try_enable_console() in 7th patch. The resulting code is the same as in v3. This 2nd move was not needed in v3 because the code was moved to this final location later. [Petr] + Switch order of the 10th and 11th patch. Aka make try_enable_default_console() return an err before refactoring try_enable_console() call try_enable_preferred_console() only when there is any. [Petr] + Initialize err value in try_enable_console() in 11th patch. It prevents using a non-initialized variable. [AI:gemini-3] + Make sure that pre-enabled consoles won't get registered when something went wrong in try_enable_console() in 11th patch [Petr] Changes against [v2]: + Move static_assert() after declaration (1st patch) [Steven] + Rename update_preferred_console() to add_or_update_preferred_console() [John] + WARN_ON() when called without "name" and "devname" [John] + print error when reached MAX_PREFERRED_CONSOLES + Add comment above code adding new entries [John] (all in 4th patch) + Call console->setup() under console_lock() in braille_register_console() (new patch) [Sashiko] + Use "No functional changes." phrase in commit messages. [Steven] + Call try_enable_preferred_console() only when there is no preferred console (reworked and split 9th patch) [Petr] + Added taken Reviewed-by and Acked-by tags [John, Macros] Changes against [v1]: + Fix stale comment (1st patch, Chris) + Add comment descibing update_preferred_console() behavior (3rd patch, John) + Better describe behavior changes caused by update_preferred_console() in the commit message (3rd patch, Chris) + Use unsigned int for iterating/indexing preferred_consoles[] table (3rd patch, John) + Add a check preventing an update via "devname" is already assigned to a real "name". (3rd patch, Petr) + Use only Braille entries when trying to enable Braille console (Chris) + Split all try_enable_*console() calls into new try_enable_console() and return early when try_enable_braille_console() succeeded. Note that we do not longer need to initialize "err" variable in this case. (new 5th patch, Chris, Petr) + Put back the explicit check of CON_BRL flag in register_console() so that it returns prelimitary only when the driver is used in Braille mode. (6th patch, Chris, Petr) + Add comments explaining that try_enable_braille_console() might succeeded also when newcon->match() succeeded. In this case, the Braille mode can't be used because the console device was already used as an early console.[*] (6th patch, Chris, Petr) + Reset preferred_dev_console_prev when used to revert the value. (7th patch, John) + Add Acked-by and Reviewed-by tags (1st, 2nd, 4th patch, Chris, Marcos) [v1] https://lore.kernel.org/r/20260206165002.496724-1-pmladek@suse.com [v2] https://lore.kernel.org/r/20260423130015.85175-1-pmladek@suse.com [v3] https://lore.kernel.org/r/20260602085312.228251-1-pmladek@suse.com [v4] https://lore.kernel.org/r/20260604101459.393162-1-pmladek@suse.com [v5] https://lore.kernel.org/r/20260929120546.328616-1-pmladek@suse.com Petr Mladek (16): printk: Rename struct console_cmdline to preferred_console printk: Rename preferred_console to preferred_dev_console printk: Cleanup _braille_(un)register_console() wrappers printk: Separate code for adding/updating preferred console metadata printk: Do not accept an empty name or devname as a preferred console printk: Prefer the console either via name or devname exclusively printk: Check that index is not defined when a console is preferred via devname printk: Ensure consistent name and devname when updating preferred console printk: Do not quietly ignore adding entry for a preferred console when there is no space printk: Allow to debug misuse of add_or_update_preferred_console() console/braille: Lock console->setup() call during the registration printk: Separate code for enabling console printk: Try to register each console as Braille first printk: Do not set Braille console as preferred_console printk: Modify try_enable_default_console() to return error/success printk: Try enable preferred consoles only when there are any .../accessibility/braille/braille_console.c | 17 +- include/linux/console.h | 1 + kernel/printk/braille.c | 20 +- kernel/printk/braille.h | 22 +- .../{console_cmdline.h => console_register.h} | 9 +- kernel/printk/printk.c | 429 ++++++++++++------ 6 files changed, 338 insertions(+), 160 deletions(-) rename kernel/printk/{console_cmdline.h => console_register.h} (74%) -- 2.56.0