linux-kernel - [PATCH 0/3] tty: fix input-speed handling

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Message-Id: <20180715133935.24964-1-johan@kernel.org>
Date:   Sun, 15 Jul 2018 15:39:32 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jslaby@...e.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: [PATCH 0/3] tty: fix input-speed handling

Turns out we had some long-standing bugs in how we handle termios input
speeds. Specifically, we could end up setting the CIBAUD bits despite
the user leaving them cleared (i.e. B0, which means that we use the same
input and output rate). And once any of these bits were set we failed to
clear them on later updates, leading to incorrect rates being reported
back to user space.

Both issues could lead to an unexpected input rate being set on
subsequent termios updates unless the user actively clears CIBAUD.

Fortunately, no in-tree tty driver seems to use the input speed for
anything but to suppress line-setting updates, so the impact of this
should be mostly limited to the CIBAUD bits sometimes being incorrectly
set in returned termios data.

The final patch cleans up the conditional compilation of the BOTHER and
CIBAUD functionality by not having the latter depend on the former.

Johan

Johan Hovold (3):
  tty: fix termios input-speed encoding
  tty: fix termios input-speed encoding when using BOTHER
  tty: support CIBAUD without BOTHER

 drivers/tty/tty_baudrate.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

-- 
2.18.0