[Devel] [PATCH RHEL9 COMMIT] ms/tty: Remove baudrate dead code & make ktermios params const

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-284.25.1.vz9.30.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-284.25.1.vz9.30.10
------>
commit a485abe5e4d26a162d7864ebc4184127111ac0fe
Author: Ilpo Järvinen <ilpo.jarvinen at linux.intel.com>
Date:   Tue Aug 16 14:57:32 2022 +0300

    ms/tty: Remove baudrate dead code & make ktermios params const
    
    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.
    
    Reviewed-by: Andy Shevchenko <andy.shevchenko at gmail.com>
    Signed-off-by: Ilpo Järvinen <ilpo.jarvinen at linux.intel.com>
    Link: https://lore.kernel.org/r/20220816115739.10928-2-ilpo.jarvinen@linux.intel.com
    Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
    
    Getting rid of compilation warnings.
    
    https://virtuozzo.atlassian.net/browse/PSBM-148793
    
    Feature: fix ms/drivers
    
    (cherry picked from commit 87888fb9ac0c71cdc1edd0779382052475dadb84)
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 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 426b1252781a..e1d3c68a0b2c 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;
 
@@ -68,11 +68,7 @@ speed_t tty_termios_baud_rate(struct ktermios *termios)
 #endif
 	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];
 }
@@ -84,13 +80,13 @@ 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)
 {
 #ifdef IBSHIFT
 	unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
@@ -104,11 +100,7 @@ speed_t tty_termios_input_baud_rate(struct ktermios *termios)
 #endif
 	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];
 #else	/* IBSHIFT */
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 33572a5a5538..71bff77266f1 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -474,7 +474,7 @@ extern int tty_hung_up_p(struct file *filp);
 extern void do_SAK(struct tty_struct *tty);
 extern void __do_SAK(struct tty_struct *tty);
 extern void no_tty(void);
-extern speed_t tty_termios_baud_rate(struct ktermios *termios);
+extern speed_t tty_termios_baud_rate(const struct ktermios *termios);
 extern void tty_termios_encode_baud_rate(struct ktermios *termios,
 						speed_t ibaud, speed_t obaud);
 extern void tty_encode_baud_rate(struct tty_struct *tty,