[PATCH tty-next v1 2/4] serial: 8250: Do not set UART_LSR_THRE in @read_status_mask

From: John Ogness
Date: Mon Dec 16 2024 - 12:13:19 EST


Since Linux 2.1.8 @read_status_mask is no longer used as a
general control of which bits are used from the LSR register.
Instead it has become an additional mask applied to
@ignore_status_mask. Since UART_LSR_THRE is never set for
@ignore_status_mask, it serves no purpose to set it for
@read_status_mask. In fact, it propagates the misconception
that @read_status_mask can be used as a general mask for LSR
bits.

Do not set UART_LSR_THRE for @read_status_mask.

Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_omap.c | 2 +-
drivers/tty/serial/8250/8250_port.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 9eb9aa766811..5290aed76a5e 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -412,7 +412,7 @@ static void omap_8250_set_termios(struct uart_port *port,
*/
uart_update_timeout(port, termios->c_cflag, baud);

- up->port.read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
+ up->port.read_status_mask = UART_LSR_OE | UART_LSR_DR;
if (termios->c_iflag & INPCK)
up->port.read_status_mask |= UART_LSR_FE | UART_LSR_PE;
if (termios->c_iflag & (IGNBRK | PARMRK))
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 4d742bfb7e9a..a5c1b069c67b 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2786,7 +2786,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
*/
uart_update_timeout(port, termios->c_cflag, baud);

- port->read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
+ port->read_status_mask = UART_LSR_OE | UART_LSR_DR;
if (termios->c_iflag & INPCK)
port->read_status_mask |= UART_LSR_FE | UART_LSR_PE;
if (termios->c_iflag & (IGNBRK | BRKINT | PARMRK))
--
2.39.5