linux-kernel - Re: [PATCH][V2] drm/i915/guc: fix GEM_BUG

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Message-ID: <87d0ww2was.fsf@intel.com>
Date:   Tue, 12 Jun 2018 12:23:07 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Colin King <colin.king@...onical.com>
Cc:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V2] drm/i915/guc: fix GEM_BUG_ON check

On Tue, 12 Jun 2018, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> On Mon, Jun 11, 2018 at 05:46:53PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>> 
>> The check for level being less than zero always false because flags
>> is currently unsigned and can never be negative. Fix this by making
>> flags a s32.
>> 
>> Detected by CoverityScan, CID#1468363 ("Macro compares unsigned to 0")
>> 
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> 
>> ---
>> V2: Make flags s32 rather than remove the GEM_BUG_ON check, thanks to
>> Ville Syrjälä for spotting the mistake in my first attempt.
>> ---
>>  drivers/gpu/drm/i915/intel_guc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_guc.c b/drivers/gpu/drm/i915/intel_guc.c
>> index 116f4ccf1bbd..fb31f5004bcf 100644
>> --- a/drivers/gpu/drm/i915/intel_guc.c
>> +++ b/drivers/gpu/drm/i915/intel_guc.c
>> @@ -206,7 +206,7 @@ void intel_guc_fini(struct intel_guc *guc)
>>  static u32 get_log_control_flags(void)
>>  {
>>  	u32 level = i915_modparams.guc_log_level;
>> -	u32 flags = 0;
>> +	s32 flags = 0;
>>  
>>  	GEM_BUG_ON(level < 0);
>
> Only insane people use "s32" when it's not part of the hardware spec and
> you changed the wrong variable...

Yeah, int level.

Also,

Fixes: cb5d64e9f13e ("drm/i915/guc: Allow user to control default GuC logging")

BR,
Jani.


>
> regards,
> dan carpenter
>

-- 
Jani Nikula, Intel Open Source Graphics Center