linux-kernel - Re: [PATCH] char: mwave: smapi: Make usSmapiOK signed to fix warning

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Message-ID: <927ff3f8-8814-4f95-ab85-0e0c14c6ed85@gmail.com>
Date: Thu, 17 Apr 2025 11:29:20 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: arnd@...db.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] char: mwave: smapi: Make usSmapiOK signed to fix warning

On 15/04/25 20:22, Greg KH wrote:
> On Thu, Apr 10, 2025 at 02:49:29AM +0530, Purva Yeshi wrote:
>> Fix Smatch-detected warning:
>> drivers/char/mwave/smapi.c:69 smapi_request() warn:
>> assigning (-5) to unsigned variable 'usSmapiOK'
>>
>> Assigning a negative value (-EIO, which is -5) to an unsigned short
>> (usSmapiOK) causes a Smatch warning because negative values cannot
>> be correctly represented in an unsigned type, leading to unexpected
>> behavior.
>>
>> Change the type of usSmapiOK from unsigned short to short to allow
>> storing negative values like -EIO without causing a type mismatch or
>> logic error.
>>
>> Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
>> ---
>>   drivers/char/mwave/smapi.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/mwave/smapi.c b/drivers/char/mwave/smapi.c
>> index f8d79d393b69..37da1339357e 100644
>> --- a/drivers/char/mwave/smapi.c
>> +++ b/drivers/char/mwave/smapi.c
>> @@ -66,7 +66,7 @@ static int smapi_request(unsigned short inBX, unsigned short inCX,
>>   	unsigned short myoutDX = 5, *pmyoutDX = &myoutDX;
>>   	unsigned short myoutDI = 6, *pmyoutDI = &myoutDI;
>>   	unsigned short myoutSI = 7, *pmyoutSI = &myoutSI;
>> -	unsigned short usSmapiOK = -EIO, *pusSmapiOK = &usSmapiOK;
>> +	short usSmapiOK = -EIO, *pusSmapiOK = &usSmapiOK;
> 
> This no longer a "us" variable type :(
> 
> The joy of using this type of notation, ick.  Please fix this up to use
> an explicit type (like s16), and fix the variable name at the same time.
> 
> thanks,
> 
> greg k-h

Hi Greg,

Thanks for the feedback.

I’ll update the patch to use an explicit s16 type and rename the 
usSmapiOK with SmapiOK to match the new type. I’ll send a v2 shortly.

Best regards,
Purva