linux-kernel - Re: [PATCH] drm/amd/pm: clean up redundant comparisons with 0

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Message-ID: <f98d840d-f3ff-47e1-b609-2cfe33c65cb5@roeck-us.net>
Date:   Tue, 7 Nov 2023 10:03:47 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     José Pekkarinen <jose.pekkarinen@...hound.fi>
Cc:     evan.quan@....com, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com,
        skhan@...uxfoundation.org, airlied@...il.com, daniel@...ll.ch,
        jdelvare@...e.com, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH] drm/amd/pm: clean up redundant comparisons with 0

On 11/7/23 09:26, José Pekkarinen wrote:
> On 2023-11-07 16:08, Guenter Roeck wrote:
>> On 11/7/23 00:29, José Pekkarinen wrote:
>>> There is a couple of function return checks of functions that return
>>> unsigned values, and local variables to hold them are also unsigned, so
>>> checking if they are negative will always return false. This patch will
>>> remove them, as well as the never reached code.
>>>
>>> drivers/gpu/drm/amd/pm/amdgpu_pm.c:2801:5-8: WARNING: Unsigned expression compared with zero: val < 0
>>> drivers/gpu/drm/amd/pm/amdgpu_pm.c:2814:5-8: WARNING: Unsigned expression compared with zero: val < 0
>>>
>>> Signed-off-by: José Pekkarinen <jose.pekkarinen@...hound.fi>
>>> ---
>>>   drivers/gpu/drm/amd/pm/amdgpu_pm.c | 4 ----
>>>   1 file changed, 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/pm/amdgpu_pm.c b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
>>> index 8bb2da13826f..e7bb1d324084 100644
>>> --- a/drivers/gpu/drm/amd/pm/amdgpu_pm.c
>>> +++ b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
>>> @@ -2798,8 +2798,6 @@ static ssize_t amdgpu_hwmon_show_power_avg(struct device *dev,
>>>       unsigned int val;
>>>         val = amdgpu_hwmon_get_power(dev, AMDGPU_PP_SENSOR_GPU_AVG_POWER);
>>> -    if (val < 0)
>>> -        return val;
>>>
>>
>> This is reporting errors returned from amdgpu_hwmon_get_power() as
>> large integers.
> 
>      Alright, that case it is a false positive, thanks for the comment!
> 


No, it isn't a false positive. The fix is wrong. The variable should be declared
'int val', not 'unsigned int val'.

Guenter