linux-kernel - Re: commit 5fe212364 causes division by zero with large bauds

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Message-ID: <20130912122135.GP10105@radagast>
Date:	Thu, 12 Sep 2013 07:21:35 -0500
From:	Felipe Balbi <balbi@...com>
To:	Alexey Pelykh <alexey.pelykh@...il.com>
CC:	<balbi@...com>, Tony Lindgren <tony@...mide.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	<linux-serial@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: commit 5fe212364 causes division by zero with large bauds

Hi,

On Thu, Sep 12, 2013 at 07:37:07AM +0300, Alexey Pelykh wrote:
> Actually, here it is, but not formatted properly
>
> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> index 816d1a2..146e712 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -240,14 +240,14 @@ serial_omap_baud_is_mode16(struct uart_port
> *port, unsigned int baud)
>  {
>   unsigned int n13 = port->uartclk / (13 * baud);
>   unsigned int n16 = port->uartclk / (16 * baud);
> - int baudAbsDiff13 = baud - (port->uartclk / (13 * n13));
> - int baudAbsDiff16 = baud - (port->uartclk / (16 * n16));
> + int baudAbsDiff13 = n13 ? (baud - (port->uartclk / (13 * n13))) : INT_MAX;
> + int baudAbsDiff16 = n16 ? (baud - (port->uartclk / (16 * n16))) : INT_MAX;
>   if(baudAbsDiff13 < 0)
>   baudAbsDiff13 = -baudAbsDiff13;
>   if(baudAbsDiff16 < 0)
>   baudAbsDiff16 = -baudAbsDiff16;
> 
> - return (baudAbsDiff13 > baudAbsDiff16);
> + return (baudAbsDiff13 >= baudAbsDiff16);
>  }
> 
>  /*
> @@ -258,13 +258,13 @@ serial_omap_baud_is_mode16(struct uart_port
> *port, unsigned int baud)
>  static unsigned int
>  serial_omap_get_divisor(struct uart_port *port, unsigned int baud)
>  {
> - unsigned int divisor;
> + unsigned int mode;
> 
>   if (!serial_omap_baud_is_mode16(port, baud))
> - divisor = 13;
> + mode = 13;
>   else
> - divisor = 16;
> - return port->uartclk/(baud * divisor);
> + mode = 16;
> + return port->uartclk/(mode * baud);
>  }
> 
>  static void serial_omap_enable_ms(struct uart_port *port)

looks good to me, but I'd split it as suggested as a reply to previous
email.

-- 
balbi

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