linux-kernel - Re: [PATCH] iio: addac: ad74115: Fix use of uninitialized variable rate

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Message-ID: <b9add3a4-9ec8-489f-9390-29d6ed49ba14@gmail.com>
Date: Thu, 10 Apr 2025 23:07:43 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: David Lechner <dlechner@...libre.com>, cosmin.tanislav@...log.com,
 lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: addac: ad74115: Fix use of uninitialized variable
 rate

On 10/04/25 20:21, David Lechner wrote:
> On 4/9/25 3:29 PM, Purva Yeshi wrote:
>> Fix Smatch-detected error:
>> drivers/iio/addac/ad74115.c:823 _ad74115_get_adc_code() error:
>> uninitialized symbol 'rate'.
>>
>> The variable rate was declared but not given any value before being used
>> in a division. If the code reached that point without setting rate, it
>> would cause unpredictable behavior.
>>
>> Declare and initialize 'rate' to zero inside the 'else' block where it is
>> used. This ensures 'rate' is always initialized before being passed to
>> DIV_ROUND_CLOSEST.
>>
>> Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
>> ---
>>   drivers/iio/addac/ad74115.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/addac/ad74115.c b/drivers/iio/addac/ad74115.c
>> index a7e480f2472d..26770c68e5fa 100644
>> --- a/drivers/iio/addac/ad74115.c
>> +++ b/drivers/iio/addac/ad74115.c
>> @@ -814,7 +814,7 @@ static int _ad74115_get_adc_code(struct ad74115_state *st,
>>   			return -ETIMEDOUT;
>>   	} else {
>>   		unsigned int regval, wait_time;
>> -		int rate;
>> +		int rate = 0;
>>   
>>   		ret = ad74115_get_adc_rate(st, channel, &rate);
>>   		if (ret < 0)
> 
> I don't see how rate could be used uninitialized since we are
> returning the error if ad74115_get_adc_rate() fails.
> 
> Also, initializing to 0 would then cause a divide by 0 error
> if that value was actually used later in the code.

Hi,

Thank you for the review and explanation.

Understood — since there's a risk of misuse later (like divide-by-zero), 
it's best to leave it as is.

Best regards,
Purva

> 
>