[PATCH 1/8] tty: Remove baudrate dead code & make ktermios params const

From: Ilpo Järvinen
Date: Tue Aug 16 2022 - 08:08:43 EST


With the architectures currently in-tree, either:
1) CBAUDEX is zero
2) The earlier BOTHER if check covers cbaud < 1 case
3) All CBAUD bits are covered by the baud_table

Thus, the check for cbaud being out-of-range for CBAUDEX case cannot
ever be true.

The ktermios parameters can now be made const.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
drivers/tty/tty.h | 2 +-
drivers/tty/tty_baudrate.c | 24 ++++++++----------------
include/linux/tty.h | 2 +-
3 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/drivers/tty/tty.h b/drivers/tty/tty.h
index f310a8274df1..1c08c9b67b16 100644
--- a/drivers/tty/tty.h
+++ b/drivers/tty/tty.h
@@ -73,7 +73,7 @@ void tty_buffer_set_lock_subclass(struct tty_port *port);
bool tty_buffer_restart_work(struct tty_port *port);
bool tty_buffer_cancel_work(struct tty_port *port);
void tty_buffer_flush_work(struct tty_port *port);
-speed_t tty_termios_input_baud_rate(struct ktermios *termios);
+speed_t tty_termios_input_baud_rate(const struct ktermios *termios);
void tty_ldisc_hangup(struct tty_struct *tty, bool reset);
int tty_ldisc_reinit(struct tty_struct *tty, int disc);
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
diff --git a/drivers/tty/tty_baudrate.c b/drivers/tty/tty_baudrate.c
index 3cd99ed7c710..4e3fd756dfc7 100644
--- a/drivers/tty/tty_baudrate.c
+++ b/drivers/tty/tty_baudrate.c
@@ -49,13 +49,13 @@ static int n_baud_table = ARRAY_SIZE(baud_table);
*
* Convert termios baud rate data into a speed. This should be called
* with the termios lock held if this termios is a terminal termios
- * structure. May change the termios data. Device drivers can call this
- * function but should use ->c_[io]speed directly as they are updated.
+ * structure. Device drivers can call this function but should use
+ * ->c_[io]speed directly as they are updated.
*
* Locking: none
*/

-speed_t tty_termios_baud_rate(struct ktermios *termios)
+speed_t tty_termios_baud_rate(const struct ktermios *termios)
{
unsigned int cbaud;

@@ -67,11 +67,7 @@ speed_t tty_termios_baud_rate(struct ktermios *termios)

if (cbaud & CBAUDEX) {
cbaud &= ~CBAUDEX;
-
- if (cbaud < 1 || cbaud + 15 > n_baud_table)
- termios->c_cflag &= ~CBAUDEX;
- else
- cbaud += 15;
+ cbaud += 15;
}
return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
}
@@ -83,13 +79,13 @@ EXPORT_SYMBOL(tty_termios_baud_rate);
*
* Convert termios baud rate data into a speed. This should be called
* with the termios lock held if this termios is a terminal termios
- * structure. May change the termios data. Device drivers can call this
- * function but should use ->c_[io]speed directly as they are updated.
+ * structure. Device drivers can call this function but should use
+ * ->c_[io]speed directly as they are updated.
*
* Locking: none
*/

-speed_t tty_termios_input_baud_rate(struct ktermios *termios)
+speed_t tty_termios_input_baud_rate(const struct ktermios *termios)
{
unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;

@@ -102,11 +98,7 @@ speed_t tty_termios_input_baud_rate(struct ktermios *termios)

if (cbaud & CBAUDEX) {
cbaud &= ~CBAUDEX;
-
- if (cbaud < 1 || cbaud + 15 > n_baud_table)
- termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
- else
- cbaud += 15;
+ cbaud += 15;
}
return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 7b0a5d478ef6..cf5ab26de73d 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -434,7 +434,7 @@ int tty_hung_up_p(struct file *filp);
void do_SAK(struct tty_struct *tty);
void __do_SAK(struct tty_struct *tty);
void no_tty(void);
-speed_t tty_termios_baud_rate(struct ktermios *termios);
+speed_t tty_termios_baud_rate(const struct ktermios *termios);
void tty_termios_encode_baud_rate(struct ktermios *termios, speed_t ibaud,
speed_t obaud);
void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud,
--
2.30.2