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Commit 20620d68 authored by David Woodhouse's avatar David Woodhouse Committed by Linus Torvalds
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serial: don't optimise away baud rate changes when BOTHER is used 



The uart_set_termios() function will bail out early without bothering to
touch the hardware, if it decides that nothing "relevant" has changed.
Unfortunately, its idea of "relevant" doesn't include c_[io]speed.  So if
the baud rate bits are BOTHER and you just change the speed, the change
gets optimised away.

This patch makes it ignore the old Bfoo bits in c_cflag and just check
whether c_ispeed and c_ospeed have changed.  Those integers are always set
appropriately for us by set_termios().

Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
Acked-by: default avatarAlan Cox <alan@redhat.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 187226f5

drivers/serial/serial_core.c

+5 −2
Original line number Diff line number Diff line
@@ -1146,11 +1146,14 @@ static void uart_set_termios(struct tty_struct *tty, struct ktermios *old_termio 


	/*

	 * These are the bits that are used to setup various

	 * flags in the low level driver.

	 * flags in the low level driver. We can ignore the Bfoo

	 * bits in c_cflag; c_[io]speed will always be set

	 * appropriately by set_termios() in tty_ioctl.c

	 */

#define RELEVANT_IFLAG(iflag)	((iflag) & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))



	if ((cflag ^ old_termios->c_cflag) == 0 &&

	    tty->termios->c_ospeed == old_termios->c_ospeed &&

	    tty->termios->c_ispeed == old_termios->c_ispeed &&

	    RELEVANT_IFLAG(tty->termios->c_iflag ^ old_termios->c_iflag) == 0)

		return;