linux-kernel - Re: [patch] regulator: max77686: fix a shift wrapping bug

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Date:	Fri, 15 May 2015 10:10:26 -0700
From:	Joe Perches <joe@...ches.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] regulator: max77686: fix a shift wrapping bug

On Fri, 2015-05-15 at 19:19 +0900, Chanwoo Choi wrote:
> On 05/15/2015 06:25 PM, Dan Carpenter wrote:
> > We need to be able to handle more than 32 bits here because "id" can go
> > up to MAX77686_BUCK9 (34).  ->gpio_enabled is a u64 so that's fine
> > already.
> > 
> > Fixes: 3307e9025d29 ('regulator: max77686: Add GPIO control')
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Alternate suggested patch below:

> > diff --git a/drivers/regulator/max77686.c b/drivers/regulator/max77686.c
[]
> > @@ -121,7 +121,7 @@ static unsigned int max77686_map_normal_mode(struct max77686_data *max77686,
> > -		if (max77686->gpio_enabled & (1 << id))
> > +		if (max77686->gpio_enabled & (1ULL << id))
[]
> > @@ -277,7 +277,7 @@ static int max77686_of_parse_cb(struct device_node *np,
> >  	if (gpio_is_valid(config->ena_gpio)) {
> > -		max77686->gpio_enabled |= (1 << desc->id);
> > +		max77686->gpio_enabled |= (1ULL << desc->id);
[]
> Looks good to me.
> Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

This could be better with DECLARE_BITMAP and test_bit/set_bit
---

 drivers/regulator/max77686.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/regulator/max77686.c b/drivers/regulator/max77686.c
index 23b7c06..17ccf36 100644
--- a/drivers/regulator/max77686.c
+++ b/drivers/regulator/max77686.c
@@ -88,7 +88,7 @@ enum max77686_ramp_rate {
 };
 
 struct max77686_data {
-	u64 gpio_enabled:MAX77686_REGULATORS;
+	DECLARE_BITMAP(gpio_enabled, MAX77686_REGULATORS);
 
 	/* Array indexed by regulator id */
 	unsigned int opmode[MAX77686_REGULATORS];
@@ -121,7 +121,7 @@ static unsigned int max77686_map_normal_mode(struct max77686_data *max77686,
 	case MAX77686_BUCK8:
 	case MAX77686_BUCK9:
 	case MAX77686_LDO20 ... MAX77686_LDO22:
-		if (max77686->gpio_enabled & (1 << id))
+		if (test_bit(id, max77686->gpio_enabled))
 			return MAX77686_GPIO_CONTROL;
 	}
 
@@ -277,7 +277,7 @@ static int max77686_of_parse_cb(struct device_node *np,
 	}
 
 	if (gpio_is_valid(config->ena_gpio)) {
-		max77686->gpio_enabled |= (1 << desc->id);
+		set_bit(desc->id, max77686->gpio_enabled);
 
 		return regmap_update_bits(config->regmap, desc->enable_reg,
 					  desc->enable_mask,



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