uart_port_tx_limited(9)

hi bestie! welcome to the uart_port_tx_limited(9) page from the Kernel API Manual — it's giving iconic kernel helper energy and we're gonna get through it together 💖✨

🌸 NAME 🌸

uart_port_tx_limited - - transmit helper for uart_port with count limiting 💅

✨ SYNOPSIS ✨

uart_port_tx_limited (port , ch , count , tx_ready , put_char , tx_done );

🎀 ARGUMENTS 🎀

• port — uart port
• ch — variable to store a character to be written to the HW
• count — a limit of characters to send
• tx_ready — can HW accept more data function
• put_char — function to write a character
• tx_done — function to call after the loop is done

💖 DESCRIPTION 💖

okay so bestie, this helper literally transmits characters from the xmit buffer to the hardware using put_char. It does so until count characters are sent and while tx_ready evaluates to true. no cap.

The expression in macro parameters shall be designed as follows:

• tx_ready: should evaluate to true if the HW can accept more data to be sent. This parameter can be true, which means the HW is always ready.
• put_char: shall write ch to the device of port.
• tx_done: when the write loop is done, this can perform arbitrary action before potential invocation of ops->stop_tx happens. If the driver does not need to do anything, use e.g. ({}).

For all of them, port->lock is held, interrupts are locally disabled and the expressions must not sleep. (like, seriously, do not sleep, bestie 😴🚫)

🌈 RETURN 🌈

the number of characters in the xmit buffer when done. periodt. 👑

🦋 SEE ALSO 🦋

• Kernel file ./include/linux/serial_core.h struct uart_ops(9)
• uart_port_set_cons(9)
• uart_port_lock(9)
• uart_port_lock_irq(9)
• uart_port_lock_irqsave(9)
• uart_port_trylock(9)
• uart_port_trylock_irqsave(9)
• uart_port_unlock(9)
• uart_port_unlock_irq(9)
• uart_port_unlock_irqrestore(9)
• enum uart_pm_state(9)
• uart_xmit_advance(9)
• enum UART_TX_FLAGS(9)
• uart_port_tx_limited_flags(9)
• uart_port_tx(9)
• uart_port_tx_flags(9)

catch u later bestie! this page is from ./include/linux, dated October 2026, and it's uart_port_tx_limited(9) out. 💅✨🫶