linux-kernel - Re: [PATCH][next] iio: addac: ad74115: remove redundant if statement

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Date: Thu, 28 Mar 2024 17:14:32 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Colin Ian King <colin.i.king@...il.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Cosmin Tanislav <cosmin.tanislav@...log.com>,
	Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] iio: addac: ad74115: remove redundant if statement

On Thu, Mar 28, 2024 at 02:52:43PM +0100, Nuno Sá wrote:
> Hi Colin,
> 
> Thanks for your patch...
> 
> On Thu, 2024-03-28 at 11:22 +0000, Colin Ian King wrote:
> > The if statement is redundant because the variable i being
> > assigned in the statement is never read afterwards. Remove it.
> > 
> > Cleans up clang scan build warning:
> > drivers/iio/addac/ad74115.c:570:3: warning: Value stored to 'i'
> > is never read [deadcode.DeadStores]
> > 
> > Signed-off-by: Colin Ian King <colin.i.king@...il.com>
> > ---
> >  drivers/iio/addac/ad74115.c | 3 ---
> >  1 file changed, 3 deletions(-)
> > 
> > diff --git a/drivers/iio/addac/ad74115.c b/drivers/iio/addac/ad74115.c
> > index e6bc5eb3788d..d31d4adb017e 100644
> > --- a/drivers/iio/addac/ad74115.c
> > +++ b/drivers/iio/addac/ad74115.c
> > @@ -566,9 +566,6 @@ static int ad74115_set_comp_debounce(struct ad74115_state *st,
> > unsigned int val)
> >  		if (val <= ad74115_debounce_tbl[i])
> >  			break;
> >  
> > -	if (i == len)
> > -		i = len - 1;
> > -
> 
> Hmm, this change is clearly good but I think we're actually missing the proper fix in
> here. I'm being lazy and not checking the datasheet and Cosmin can further comment.
> But I'm fairly sure that the intent of the code is actually to use i in the call to
> regmap_update_bits(). I mean if we look at the mask AD74115_DIN_DEBOUNCE_MASK and the
> possible values of val...

Good eye.  I haven't looked at the datasheet either, but logically I
would think you go until you hit something that is too high and then
step back to the valid valies.  In other words the <= should be < and
the i = len - 1 should just be i--.

(The first element in the ad74115_debounce_tbl[] array is zero btw, so
it's never going to break with i == 0).

regards,
dan carpenter

diff --git a/drivers/iio/addac/ad74115.c b/drivers/iio/addac/ad74115.c
index e6bc5eb3788d..8d484cefe5ff 100644
--- a/drivers/iio/addac/ad74115.c
+++ b/drivers/iio/addac/ad74115.c
@@ -559,19 +559,16 @@ static void ad74115_gpio_set(struct gpio_chip *gc, unsigned int offset, int valu
 
 static int ad74115_set_comp_debounce(struct ad74115_state *st, unsigned int val)
 {
-	unsigned int len = ARRAY_SIZE(ad74115_debounce_tbl);
 	unsigned int i;
 
-	for (i = 0; i < len; i++)
-		if (val <= ad74115_debounce_tbl[i])
+	for (i = 0; i < ARRAY_SIZE(ad74115_debounce_tbl); i++)
+		if (ad74115_debounce_tbl[i] > val)
 			break;
-
-	if (i == len)
-		i = len - 1;
+	i--;
 
 	return regmap_update_bits(st->regmap, AD74115_DIN_CONFIG1_REG,
 				  AD74115_DIN_DEBOUNCE_MASK,
-				  FIELD_PREP(AD74115_DIN_DEBOUNCE_MASK, val));
+				  FIELD_PREP(AD74115_DIN_DEBOUNCE_MASK, ad74115_debounce_tbl[i]));
 }
 
 static int ad74115_comp_gpio_get_direction(struct gpio_chip *chip,