Sparse errors

[Pierre-Louis Bossart]

On 5/26/21 2:40 AM, Takashi Iwai wrote:
> On Tue, 25 May 2021 21:32:27 +0200,
> Pierre-Louis Bossart wrote:
>>
>> Hi Takashi,
>> Sparse reports a lot of new issues in our last checks with more options:
>>
>> export ARCH=x86_64 CF="-Wsparse-error -Wsparse-all
>> -Wno-bitwise-pointer -Wno-pointer-arith -Wno-typesign -Wnoshadow
>> -Wno-sizeof-bool"
>> make -k sound/ C=2
>>
>> most are linked to the __user and pcm_format_t restricted types, but I
>> found the simpler ones below which are useless comparisons. I can send
>> a patch for the last but not sure how to address the first two.
>>
>> Thanks for your feedback
>> -Pierre
>>
>> sound/core/info.c:95:38: error: self-comparison always evaluates to false
>>
>> 	if (pos < 0 || (long) pos != pos || (ssize_t) count < 0)
>> 		return false;
>>
>> not sure what the second comparison is meant to check?
> 
> As Dan suggested, it's a check only for 32bit architecture for a 64bit
> value.

Isn't there a better way to check this?

>> sound/drivers/opl3/opl3_midi.c:183:60: error: self-comparison always
>> evaluates to false
>>
>> This indeed makes no sense. the voice_time and vp->time are not
>> changed in the loop, the test is either redundant or something else is
>> missing.
> 
> The code doesn't look right, indeed.  It's likely meant to be vp2
> instead of vp.
> 
> --- a/sound/drivers/opl3/opl3_midi.c
> +++ b/sound/drivers/opl3/opl3_midi.c
> @@ -180,8 +180,7 @@ static int opl3_get_voice(struct snd_opl3 *opl3, int instr_4op,
>   			if (vp2->state == SNDRV_OPL3_ST_ON_2OP) {
>   				/* kill two voices, EXPENSIVE */
>   				bp++;
> -				voice_time = (voice_time > vp->time) ?
> -					voice_time : vp->time;
> +				voice_time = max(voice_time, vp2->time);
>   			}
>   		} else {
>   			/* allocate 2op voice */

It's really old code, unchanged since the first git commit in 2005... 
Are you comfortable changing this code? One of those cases where if 
people didn't notice an issue in 16+ years maybe no one cares or even 
uses this driver...

>> sound/pci/lx6464es/lx_core.c:677:34: error: self-comparison always
>> evaluates to false
>>
>> That seems like dead code indeed:
>>
>> 	u32 channels = runtime->channels;
>>
>> 	if (runtime->channels != channels)
>> 		dev_err(chip->card->dev, "channel count mismatch: %d vs %d",
>> 			   runtime->channels, channels);
> 
> Yes, this can be deleted.

I'll send a patch for this, thanks for the feedback.