diff mbox series

hwmon: (amc6821) Fix unsigned expression compared with zero

Message ID 1872639a.89.1843b5106aa.Coremail.wangkailong@jari.cn
State New
Headers
Series hwmon: (amc6821) Fix unsigned expression compared with zero |

Commit Message

KaiLong Wang Nov. 3, 2022, 2:27 a.m. UTC 
  Fix the following coccicheck warning:

drivers/hwmon/amc6821.c:215: WARNING: Unsigned expression compared
with zero: reg > 0
drivers/hwmon/amc6821.c:228: WARNING: Unsigned expression compared
with zero: reg > 0

Signed-off-by: KaiLong Wang <wangkailong@jari.cn>
---
 drivers/hwmon/amc6821.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Randy Dunlap Nov. 3, 2022, 2:59 a.m. UTC | #1 
On 11/2/22 19:27, wangkailong@jari.cn wrote:
> Fix the following coccicheck warning:
> 
> drivers/hwmon/amc6821.c:215: WARNING: Unsigned expression compared
> with zero: reg > 0
> drivers/hwmon/amc6821.c:228: WARNING: Unsigned expression compared
> with zero: reg > 0
> 
> Signed-off-by: KaiLong Wang <wangkailong@jari.cn>

Hm. IDGI. What's wrong with comparing an unsigned value to > 0?
I mean, it could be == 0 or > 0.
Please explain.

> ---
>  drivers/hwmon/amc6821.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
> index 3bfd12ff4b3c..1f5382f8d52b 100644
> --- a/drivers/hwmon/amc6821.c
> +++ b/drivers/hwmon/amc6821.c
> @@ -166,7 +166,7 @@ static struct amc6821_data *amc6821_update_device(struct device *dev)
>  	struct amc6821_data *data = dev_get_drvdata(dev);
>  	struct i2c_client *client = data->client;
>  	int timeout = HZ;
> -	u8 reg;
> +	int reg;
>  	int i;
>  
>  	mutex_lock(&data->update_lock);
Guenter Roeck Nov. 3, 2022, 2:17 p.m. UTC | #2 
On Wed, Nov 02, 2022 at 07:59:06PM -0700, Randy Dunlap wrote:
> 
> 
> On 11/2/22 19:27, wangkailong@jari.cn wrote:
> > Fix the following coccicheck warning:
> > 
> > drivers/hwmon/amc6821.c:215: WARNING: Unsigned expression compared
> > with zero: reg > 0
> > drivers/hwmon/amc6821.c:228: WARNING: Unsigned expression compared
> > with zero: reg > 0
> > 
> > Signed-off-by: KaiLong Wang <wangkailong@jari.cn>
> 
> Hm. IDGI. What's wrong with comparing an unsigned value to > 0?
> I mean, it could be == 0 or > 0.
> Please explain.

I don't get it either. The real problem with this driver is that error
returns from i2c functions are not checked. However, that problem is not
fixed by this patch. That means the patch would change behavior without
fixing the actual problem.

I wonder what kind of (broken) compiler or analyzer produces above errors.
We'll have to watch out for similar broken "fixes".

Guenter
Randy Dunlap Nov. 3, 2022, 3:03 p.m. UTC | #3 
On 11/3/22 07:17, Guenter Roeck wrote:
> On Wed, Nov 02, 2022 at 07:59:06PM -0700, Randy Dunlap wrote:
>>
>>
>> On 11/2/22 19:27, wangkailong@jari.cn wrote:
>>> Fix the following coccicheck warning:
>>>
>>> drivers/hwmon/amc6821.c:215: WARNING: Unsigned expression compared
>>> with zero: reg > 0
>>> drivers/hwmon/amc6821.c:228: WARNING: Unsigned expression compared
>>> with zero: reg > 0
>>>
>>> Signed-off-by: KaiLong Wang <wangkailong@jari.cn>
>>
>> Hm. IDGI. What's wrong with comparing an unsigned value to > 0?
>> I mean, it could be == 0 or > 0.
>> Please explain.
> 
> I don't get it either. The real problem with this driver is that error
> returns from i2c functions are not checked. However, that problem is not
> fixed by this patch. That means the patch would change behavior without
> fixing the actual problem.
> 
> I wonder what kind of (broken) compiler or analyzer produces above errors.
> We'll have to watch out for similar broken "fixes".

It says above that it's a coccicheck warning.
Guenter Roeck Nov. 3, 2022, 3:25 p.m. UTC | #4 
On Thu, Nov 03, 2022 at 08:03:35AM -0700, Randy Dunlap wrote:
> 
> 
> On 11/3/22 07:17, Guenter Roeck wrote:
> > On Wed, Nov 02, 2022 at 07:59:06PM -0700, Randy Dunlap wrote:
> >>
> >>
> >> On 11/2/22 19:27, wangkailong@jari.cn wrote:
> >>> Fix the following coccicheck warning:
> >>>
> >>> drivers/hwmon/amc6821.c:215: WARNING: Unsigned expression compared
> >>> with zero: reg > 0
> >>> drivers/hwmon/amc6821.c:228: WARNING: Unsigned expression compared
> >>> with zero: reg > 0
> >>>
> >>> Signed-off-by: KaiLong Wang <wangkailong@jari.cn>
> >>
> >> Hm. IDGI. What's wrong with comparing an unsigned value to > 0?
> >> I mean, it could be == 0 or > 0.
> >> Please explain.
> > 
> > I don't get it either. The real problem with this driver is that error
> > returns from i2c functions are not checked. However, that problem is not
> > fixed by this patch. That means the patch would change behavior without
> > fixing the actual problem.
> > 
> > I wonder what kind of (broken) compiler or analyzer produces above errors.
> > We'll have to watch out for similar broken "fixes".
> 
> It says above that it's a coccicheck warning.
> 

I see, unsigned_lesser_than_zero.cocci. It actually complains that an
unsigned variable is used to hold the return code of a function which
returns an int. In other words, it really tries to warn that the error
return code from that function is not or not properly checked.
The message is misleading for that situation.

Guenter
diff mbox series

Patch

diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
index 3bfd12ff4b3c..1f5382f8d52b 100644
--- a/drivers/hwmon/amc6821.c
+++ b/drivers/hwmon/amc6821.c
@@ -166,7 +166,7 @@  static struct amc6821_data *amc6821_update_device(struct device *dev)
 	struct amc6821_data *data = dev_get_drvdata(dev);
 	struct i2c_client *client = data->client;
 	int timeout = HZ;
-	u8 reg;
+	int reg;
 	int i;
 
 	mutex_lock(&data->update_lock);