copy_from_read_buf(9)

💅 copy_from_read_buf — NAME

okay so, copy_from_read_buf — it copies read data directly, no cap. it's a helper from the Kernel API Manual and honestly it's giving "small function, big job" energy. 🎀

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✨ SYNOPSIS ✨

bool copy_from_read_buf (const struct tty_struct *tty , u8 **kbp ,
size_t *nr );

like, yes bestie, that's the whole signature — returns a bool, takes three things, we'll get to them 💖

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🌸 ARGUMENTS 🌸

• tty — the terminal device. the main character of this whole situation 🫶
• kbp — data. that's it, that's the description, it's literally just "data" 😭
• nr — size of data. how much of it there is, so we know what we're working with ⭐

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🦋 DESCRIPTION 🦋

so this is a helper function whose whole purpose in life is to speed up n_tty_read. iconic behavior honestly. 🔥

it is only called when ICANON is off — remember that, it's a vibe check the function does not do for you — and it copies characters straight from the tty queue. no detours, no extra steps, just straight from the queue. ✨

🔒 Locking:

• called under the ldata->atomic_read_lock sem 🔐
• n_tty_read/consumer path: the caller holds a non-exclusive termios_rwsem; read_tail published 📌

bestie please respect the locking rules, they are not decorative 💀

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👑 RETURN 👑

returns true if it successfully copied data — but there is still more data to be had. so like, success with a little "...and there's more" attached 😭👑

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🌈 SEE ALSO 🌈

kernel file ./drivers/tty/n_tty.c, plus literally the whole friend group:

• n_tty_kick_worker(9), n_tty_write_wakeup(9), put_tty_queue(9), reset_buffer_flags(9)
• n_tty_flush_buffer(9), is_utf8_continuation(9), is_continuation(9)
• do_output_char(9), process_output(9), process_output_block(9)
• __process_echoes(9), add_echo_byte(9), echo_move_back_col(9), echo_set_canon_col(9)
• echo_erase_tab(9), echo_char_raw(9), echo_char(9), finish_erasing(9), eraser(9), isig(9)
• n_tty_receive_break(9), n_tty_receive_overrun(9), n_tty_receive_parity_error(9)
• n_tty_receive_char_flow_ctrl(9), n_tty_receive_char(9), n_tty_receive_buf_common(9)
• n_tty_set_termios(9), n_tty_close(9), n_tty_open(9)
• canon_copy_from_read_buf(9), job_control(9), n_tty_read(9), n_tty_write(9), n_tty_poll(9), n_tty_inherit_ops(9)

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okay that's the whole page bestie, go forth and read your tty queues responsibly 💅✨

this little number lives in ./drivers/tty, it's part of the Kernel API Manual, dated October 2026, and if you need to look it up by name it's copy_from_read_buf(9) — mwah, bye! 🎀🦋💜