mux_break_ctl(9)

📦 version 7.3.1, in nixpkgs unstable

💅 mux_break_ctl(9) — from the Kernel API Manual, bestie

Okay so before we even start: this whole page lives in the Kernel API Manual, section 9, and it's about one single little function called mux_break_ctl. Buckle up 🎀

✨ NAME ✨

mux_break_ctl — literally just "Control the transmitssion of a break signal." (and yes, it's spelled transmitssion in the original, I'm not fixing it, we don't erase history 💀)

🌸 SYNOPSIS 🌸

void mux_break_ctl (struct uart_port *port , int break_state );

That's the whole thing. Void return, two args, no cap.

🦋 ARGUMENTS 🦋

  • port — a pointer to the uart_port. You know, the struct. The main character 🌟 "Ptr to the uart_port," as the source so elegantly puts it.
  • break_state — raise it / lower it, i.e. this is the one that raises or lowers the break signal 🙌

💜 DESCRIPTION 💜

Okay so here's the tea, bestie… the Serial Mux does not support this function. That's it. That's the whole description. The entire function page exists to tell you she's booked and busy and unavailable 😭 Not a single extra behaviour described, so don't go making up headcanons about what she does. She does nothing here. Periodt. 💅

Fr fr: this is documented as unsupported for the Serial Mux — not deprecated, not undefined, just not supported. Don't come for me if you were expecting functionality, I'm just the messenger 🫶

👑 SEE ALSO 👑

The kernel file to go look at is ./drivers/tty/serial/mux.c — that's where the whole friend group lives, and honestly the roster is iconic:

All 21 of them, counted, none skipped, we ate that list UP 🍓✨

Okay that's the whole page bestie, go forth and don't call an unsupported function 💖

Sign-off szn 🎀 — this lil masterpiece comes straight out of ./drivers/tty/serial, dated October 2026, and it's filed under mux_break_ctl(9). Slay, bye! 💜🌈

📦 where this page comes from