linux-kernel - Re: [PATCH] i2c: test off by one in {piix4,vt596}

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Date:	Tue, 5 Jan 2010 17:55:11 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	Roel Kluin <roel.kluin@...il.com>
Cc:	"Ben Dooks (embedded platforms)" <ben-linux@...ff.org>,
	linux-i2c@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: test off by one in {piix4,vt596}_transaction()

On Sun, 27 Dec 2009 15:49:22 +0100, Roel Kluin wrote:
> With `while (timeout++ < MAX_TIMEOUT)' timeout reaches MAX_TIMEOUT + 1 after the loop
> This is probably unlikely to produce a problem.
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
>  drivers/i2c/busses/i2c-piix4.c  |    2 +-
>  drivers/i2c/busses/i2c-viapro.c |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
> index 1e245e9..d8e0df0 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -329,7 +329,7 @@ static int piix4_transaction(void)
>  		msleep(1);
>  
>  	/* If the SMBus is still busy, we give up */
> -	if (timeout >= MAX_TIMEOUT) {
> +	if (timeout > MAX_TIMEOUT) {
>  		dev_err(&piix4_adapter.dev, "SMBus Timeout!\n");
>  		result = -ETIMEDOUT;
>  	}
> diff --git a/drivers/i2c/busses/i2c-viapro.c b/drivers/i2c/busses/i2c-viapro.c
> index e4b1543..8a2e0d5 100644
> --- a/drivers/i2c/busses/i2c-viapro.c
> +++ b/drivers/i2c/busses/i2c-viapro.c
> @@ -168,7 +168,7 @@ static int vt596_transaction(u8 size)
>  	} while ((temp & 0x01) && (timeout++ < MAX_TIMEOUT));
>  
>  	/* If the SMBus is still busy, we give up */
> -	if (timeout >= MAX_TIMEOUT) {
> +	if (timeout > MAX_TIMEOUT) {
>  		result = -ETIMEDOUT;
>  		dev_err(&vt596_adapter.dev, "SMBus timeout!\n");
>  	}

That's right... but I'd rather change the loops to use "++timeout" and
leave the conditions as is (or maybe change it to "=="). I think it's
easier to read that way. Would that be OK with you?

-- 
Jean Delvare
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