printk_parse_prefix(9)

💖 printk_parse_prefix(9) — a Kernel API Manual moment 💖

okay so bestie, we're in the Kernel API Manual today and the star of the show is printk_parse_prefix(9). she's a little parser, she's got main character energy, and honestly? she ate.

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✨ NAME ✨

printk_parse_prefix — parse the level and the control flags. that's it, that's the whole job. 💅

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✨ SYNOPSIS ✨

u16 printk_parse_prefix (const char *text , int *level , enum
printk_info_flags *flags );

like, look at her signature. so clean. 🎀

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✨ ARGUMENTS ✨

• text — the terminated text message. yes, terminated, as in null-terminated, please don't send her a rogue unterminated string, that's not the vibe 🙈
• level — a pointer to the current level value, and she will be updating it. coming for that variable, respectfully. 🔥
• flags — a pointer to the current printk_info flags, and same deal, she's updating it too. ✨

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✨ DESCRIPTION ✨

okay so the rules of engagement, listen up 🫶

level may be NULL if the caller is genuinely not interested in the parsed value — no hard feelings, she gets it. Otherwise? the variable pointed to by level must be set to LOGLEVEL_DEFAULT in order to be updated with the parsed value. like, that's the entry fee. no LOGLEVEL_DEFAULT, no update. periodt. 💀

flags may also be NULL if you're not interested in the parsed value — also fine, also valid. Otherwise, the variable pointed to by flags will be OR'd with the parsed value. not overwritten, not replaced — OR'd. lowkey important distinction, iykyk. 🌸

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✨ RETURN ✨

she returns the length of the parsed level and control flags. the way that's literally the whole return value. iconic. 👑

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✨ SEE ALSO ✨

so. many. friends. she runs with a whole crowd 🦋 — the kernel file ./kernel/printk/printk.c plus:

• console_list_lock(9)
• console_list_unlock(9)
• console_srcu_read_lock(9)
• console_srcu_read_unlock(9)
• console_lock_spinning_enable(9)
• console_lock_spinning_disable_and_check(9)
• console_trylock_spinning(9)
• add_preferred_console(9)
• match_devname_and_update_preferred_console(9)
• console_suspend_all(9)
• console_cpu_notify(9)
• console_lock(9)
• console_trylock(9)
• console_unlock(9)
• console_flush_on_panic(9)
• printk_kthreads_shutdown(9)
• console_force_preferred_locked(9)
• pr_flush(9)
• wake_up_klogd(9)
• defer_console_output(9)
• printk_trigger_flush(9)
• printk_timed_ratelimit(9)
• kmsg_dump_register(9)
• kmsg_dump_unregister(9)
• kmsg_dump_desc(9)
• kmsg_dump_get_line(9)
• kmsg_dump_get_buffer(9)
• kmsg_dump_rewind(9)
• console_try_replay_all(9)
• __printk_cpu_sync_wait(9)
• __printk_cpu_sync_try_get(9)
• __printk_cpu_sync_put(9)

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ngl bestie, read the whole squad's pages before you go touching console locking. she's not gatekeeping but the kernel absolutely will. 😭

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💖 that's the whole page, you're so welcome 💖

this little fairy godmother of a page lives in ./kernel/printk, and the calendar says October 2026 — so go forth, parse those prefixes, and slay. 🧚‍♀️⭐🍓