Subject: Re: IRDA: mcs7780.c

From: Roel Kluin <[email-masked]>
Date: Fri, 13 Feb 2009 14:14:17 +0100

Juha Leppänen wrote:
> Hi,
> 
> In recent patch to file
> 
> drivers/net/irda/mcs7780.c

That's this one:
http://www.spinics.net/lists/netdev/msg88746.html

[PATCH] IRDA: cnt is off by 1

> I noticed when checking the code around the patch ...
> In worst case do {...} while loop is executed
> 101 times --> mcs_get_reg() is executed 101 times...
> But rval is checked only 100 times.

Right, thanks.

> If you change the order of the && expressions inside while () to
> 
> -        } while(cnt++ < 100 && (rval & MCS_IRINTX));
> +        } while((rval & MCS_IRINTX) && cnt++ < 100);

> If you also want exactly 100 maximum mcs_get_reg()
> tries ( now it is 101 ) ...

I don't think it really matters, does it?

> Happy hacking,
> Mr. Juha Leppänen
> Kuopio, Finland

You too.

------------------------------>8----------------8<------------------------------
If no prior break occurs, cnt reaches 101 after the loop, so we are still able
to change speed when cnt has become 100.

Signed-off-by: Roel Kluin <[email-masked]>
---
diff --git a/drivers/net/irda/mcs7780.c b/drivers/net/irda/mcs7780.c
index 7eafdca..8fdfb5a 100644
--- a/drivers/net/irda/mcs7780.c
+++ b/drivers/net/irda/mcs7780.c
@@ -583,9 +583,9 @@ static int mcs_speed_change(struct mcs_cb *mcs)
 
 	do {
 		mcs_get_reg(mcs, MCS_RESV_REG, &rval);
-	} while(cnt++ < 100 && (rval & MCS_IRINTX));
+	} while((rval & MCS_IRINTX) && cnt++ < 100);
 
-	if(cnt >= 100) {
+	if (cnt > 100) {
 		IRDA_ERROR("unable to change speed\n");
 		ret = -EIO;
 		goto error;