[PATCH][V2] drm/i915/guc: fix GEM_BUG_ON check

[PATCH][V2] drm/i915/guc: fix GEM_BUG_ON check

[Colin King]

From: Colin Ian King <colin.king@canonical.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@canonical.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);
 
-- 
2.17.0

Re: [PATCH][V2] drm/i915/guc: fix GEM_BUG_ON check

[Dan Carpenter]

On Mon, Jun 11, 2018 at 05:46:53PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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@canonical.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...

regards,
dan carpenter

Re: [PATCH][V2] drm/i915/guc: fix GEM_BUG_ON check

[Jani Nikula]

On Tue, 12 Jun 2018, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> On Mon, Jun 11, 2018 at 05:46:53PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.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@canonical.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