linux-kernel - Re: [PATCH][next] drm/mgag200: Fix uninitialized variable delta

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Date:   Tue, 17 Aug 2021 21:11:58 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        Dave Airlie <airlied@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] drm/mgag200: Fix uninitialized variable delta

On 17/08/2021 19:22, Thomas Zimmermann wrote:
> Hi
> 
> Am 17.08.21 um 18:32 schrieb Colin King:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> The variable delta is not initialized and this will cause unexpected
>> behaviour with the comparison of tmpdelta < delta. Fix this by setting
>> it to 0xffffffff. This matches the behaviour as in the similar function
>> mgag200_pixpll_compute_g200se_04.
>>
>> Addresses-Coverity: ("Uninitialized scalar variable")
>> Fixes: 2545ac960364 ("drm/mgag200: Abstract pixel PLL via struct
>> mgag200_pll")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> 
> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
> 
> But the commit message needs Fixes etc. I just sent out a patch for this
> issue myself. I'd like to merge both patches' tags and commit the result
> under your name. (You were first.) Is that ok for you?

Sure. Go ahead, Thanks

Colin

> 
> Best regards
> Thomas
> 
>> ---
>>   drivers/gpu/drm/mgag200/mgag200_pll.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/mgag200/mgag200_pll.c
>> b/drivers/gpu/drm/mgag200/mgag200_pll.c
>> index 7c903cf19c0d..18f1a6dd019a 100644
>> --- a/drivers/gpu/drm/mgag200/mgag200_pll.c
>> +++ b/drivers/gpu/drm/mgag200/mgag200_pll.c
>> @@ -125,6 +125,7 @@ static int mgag200_pixpll_compute_g200se_00(struct
>> mgag200_pll *pixpll, long clo
>>         m = n = p = s = 0;
>>       permitteddelta = clock * 5 / 1000;
>> +    delta = 0xffffffff;
>>         for (testp = 8; testp > 0; testp /= 2) {
>>           if (clock * testp > vcomax)
>>
>