tty_write_room(9)

💖 tty_write_room(9) 💖

okay so real talk — this one is from the Kernel API Manual, section 9, and it's literally about how much room your write queue has. bestie. the write queue. we love her. 🎀

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✨ NAME ✨

tty_write_room — write queue space. that's it. that's the whole vibe. it tells you how much space you've got to write into 🫶

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🌸 SYNOPSIS 🌸

unsigned int tty_write_room (struct tty_struct *tty );

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🦋 ARGUMENTS 🦋

• tty — the terminal. yeah. that one. the terminal you're asking about 💅

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🔥 RETURN 🔥

so it returns the number of bytes that can be queued to this device at the present time. present time!! right now!! ⏰

and here's the part where you gotta pay attention, no cap: the result should be treated as a guarantee — like, a promise — and the driver cannot offer a value it later shrinks by more than the number of bytes written. so if the driver tells you a number, it's committing. it can't be out here saying "haha jk" and taking away more than what you actually wrote. that's the deal. 🤝

⚠️ and if no method is provided, then 2K is always returned and data may be lost, because there will be no flow control. no flow control!!! 🚨 that's the cursed scenario, bestie. 2K every single time and your data just... yeets itself into the void. 😭 be aware.

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👑 SEE ALSO 👑

kernel file ./drivers/tty/tty_ioctl.c — and literally the whole friend group:

• tty_chars_in_buffer(9)
• tty_driver_flush_buffer(9)
• tty_unthrottle(9)
• tty_throttle_safe(9)
• tty_unthrottle_safe(9)
• tty_wait_until_sent(9)
• tty_termios_copy_hw(9)
• tty_termios_hw_change(9)
• tty_get_char_size(9)
• tty_get_frame_size(9)
• tty_set_termios(9)
• set_termios(9)
• set_sgttyb(9)
• tty_change_softcar(9)
• tty_mode_ioctl(9)

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okay that's the whole page, you ate that 💅✨ — this one lives at ./drivers/tty, dated October 2026, from the Kernel API Manual. go forth and respect the guarantee, fr fr 🧚💜