linux-kernel - [PATCH 3/3] tty: support CIBAUD without BOTHER

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Date:   Sun, 15 Jul 2018 15:39:35 +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 3/3] tty: support CIBAUD without BOTHER

Since commit edc6afc54968 ("[PATCH] tty: switch to ktermios and new
framework") arbitrary baud rates can be requested using BOTHER and input
rates can be requested using the termios CIBAUD bits (CBAUD shifted
IBSHIFT bits).

This functionality has been conditionally compiled depending on whether
an architecture defines BOTHER and IBSHIFT respectively, but would in
fact fail to compile unless both symbols were defined due to cross
dependencies.

Relax the IBSHIFT => BOTHER dependency so that an architecture could
theoretically support CIBAUD without the Linux-specific BOTHER, while
hopefully making the current conditional-compilation directives a bit
less confusing.

Note that the long-term goal is still to have all architectures support
both features, so an alternative could just be to have the lot depend on
BOTHER.

Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/tty/tty_baudrate.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/tty_baudrate.c b/drivers/tty/tty_baudrate.c
index 3e827a3d48d5..7576ceace571 100644
--- a/drivers/tty/tty_baudrate.c
+++ b/drivers/tty/tty_baudrate.c
@@ -100,11 +100,11 @@ speed_t tty_termios_input_baud_rate(struct ktermios *termios)

 	if (cbaud == B0)
 		return tty_termios_baud_rate(termios);
-
+#ifdef BOTHER
 	/* Magic token for arbitrary speed via c_ispeed*/
 	if (cbaud == BOTHER)
 		return termios->c_ispeed;
-
+#endif
 	if (cbaud & CBAUDEX) {
 		cbaud &= ~CBAUDEX;

@@ -114,9 +114,9 @@ speed_t tty_termios_input_baud_rate(struct ktermios *termios)
 			cbaud += 15;
 	}
 	return baud_table[cbaud];
-#else
+#else	/* IBSHIFT */
 	return tty_termios_baud_rate(termios);
-#endif
+#endif	/* IBSHIFT */
 }
 EXPORT_SYMBOL(tty_termios_input_baud_rate);

@@ -156,10 +156,11 @@ void tty_termios_encode_baud_rate(struct ktermios *termios,
 	termios->c_ispeed = ibaud;
 	termios->c_ospeed = obaud;

-#ifdef BOTHER
+#ifdef IBSHIFT
 	if ((termios->c_cflag >> IBSHIFT) & CBAUD)
 		ibinput = 1;	/* An input speed was specified */
-
+#endif
+#ifdef BOTHER
 	/* If the user asked for a precise weird speed give a precise weird
 	   answer. If they asked for a Bfoo speed they may have problems
 	   digesting non-exact replies so fuzz a bit */
-- 
2.18.0