linux-kernel - Re: [PATCH] drm/amd/display: Fix unsigned variable compared to less than zero

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Date:   Mon, 11 Nov 2019 13:27:02 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Mikita Lipski <mlipski@....com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mikita Lipski <mikita.lipski@....com>,
        Lyude Paul <lyude@...hat.com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: Fix unsigned variable compared to less
 than zero



On 11/11/19 11:46, Mikita Lipski wrote:
> 
> Thanks for catching it!
> 

Glad to help out. :)

> Reviewed-by: Mikita Lipski <mikita.lipski@....com>
> 

Thanks
--
Gustavo

> 
> On 11.11.2019 12:25, Gustavo A. R. Silva wrote:
>> Currenly, the error check below on variable*vcpi_slots*  is always
>> false because it is a uint64_t type variable, hence, the values
>> this variable can hold are never less than zero:
>>
>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c:
>> 4870         if (dm_new_connector_state->vcpi_slots < 0) {
>> 4871                 DRM_DEBUG_ATOMIC("failed finding vcpi slots: %d\n", (int)dm_new_connector_stat     e->vcpi_slots);
>> 4872                 return dm_new_connector_state->vcpi_slots;
>> 4873         }
>>
>> Fix this by making*vcpi_slots*  of int type
>>
>> Addresses-Coverity: 1487838 ("Unsigned compared against 0")
>> Fixes: b4c578f08378 ("drm/amd/display: Add MST atomic routines")
>> Signed-off-by: Gustavo A. R. Silva<gustavo@...eddedor.com>
>> ---
>>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>> index 6db07e9e33ab..a8fc90a927d6 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>> @@ -403,7 +403,7 @@ struct dm_connector_state {
>>       bool underscan_enable;
>>       bool freesync_capable;
>>       uint8_t abm_level;
>> -    uint64_t vcpi_slots;
>> +    int vcpi_slots;
>>       uint64_t pbn;
>>   };
>>   -- 2.23.0
>