linux-kernel - [PATCH 2/4] tty: omap-serial: prevent division by zero

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Date:	Mon, 15 Sep 2014 16:00:08 +0200
From:	Frans Klaver <frans.klaver@...ns.com>
To:	Tony Lindgren <tony@...mide.com>
CC:	Frans Klaver <frans.klaver@...ns.com>, Felipe Balbi <balbi@...com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexey Pelykh <alexey.pelykh@...il.com>,
	Jiri Slaby <jslaby@...e.cz>, <linux-serial@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 2/4] tty: omap-serial: prevent division by zero

If the chosen baud rate is large enough (e.g. 3.5 megabaud), the
calculated n values in calculate_baud_abs_diff may become 0. This causes
a division by zero when calculating the difference between calculated
and desired baud rates. To prevent this, cap n on 1.

Signed-off-by: Frans Klaver <frans.klaver@...ns.com>
---
 drivers/tty/serial/omap-serial.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index ae935ce..7d3f557 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -246,8 +246,12 @@ static inline int calculate_baud_abs_diff(struct uart_port *port,
 				unsigned int baud, unsigned int mode)
 {
 	unsigned int n = port->uartclk / (mode * baud);
-	int abs_diff = baud - (port->uartclk / (mode * n));
+	int abs_diff;
 
+	if (n == 0)
+		n = 1;
+
+	abs_diff = baud - (port->uartclk / (mode * n));
 	if (abs_diff < 0)
 		abs_diff = -abs_diff;
 
-- 
2.1.0

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