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

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Date:	Tue, 05 Jan 2010 22:22:23 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Jean Delvare <khali@...ux-fr.org>
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()

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>
---
> 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?

Ok,

 drivers/i2c/busses/i2c-piix4.c  |    4 ++--
 drivers/i2c/busses/i2c-viapro.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index 1e245e9..e56e4b6 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -324,12 +324,12 @@ static int piix4_transaction(void)
 	else
 		msleep(1);
 
-	while ((timeout++ < MAX_TIMEOUT) &&
+	while ((++timeout < MAX_TIMEOUT) &&
 	       ((temp = inb_p(SMBHSTSTS)) & 0x01))
 		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..a84a909 100644
--- a/drivers/i2c/busses/i2c-viapro.c
+++ b/drivers/i2c/busses/i2c-viapro.c
@@ -165,10 +165,10 @@ static int vt596_transaction(u8 size)
 	do {
 		msleep(1);
 		temp = inb_p(SMBHSTSTS);
-	} while ((temp & 0x01) && (timeout++ < MAX_TIMEOUT));
+	} 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");
 	}
--
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