Re: [PATCH] drm/i915/bxt: Fix uninitialized variables in intel_check_sprite_plane

["Maiti, Nabendu Bikash" <nabendu.bikash.maiti@intel.com>]

On 11/18/2015 7:00 PM, Ville Syrjälä wrote:
> On Wed, Nov 18, 2015 at 06:48:37PM +0530, Maiti, Nabendu Bikash wrote:
>>
>>
>> On 11/18/2015 6:22 PM, Ville Syrjälä wrote:
>>> On Wed, Nov 18, 2015 at 12:19:06PM +0000, Chris Wilson wrote:
>>>> On Wed, Nov 18, 2015 at 05:43:52PM +0530, Nabendu Maiti wrote:
>>>>> Uninitialized variables (width, Height) in intel_check_sprite_plane
>>>>> leads to compilererror in O1 level. Initialize all declared variables
>>>>> to fix this issue.
>>>>>
>>>>> Signed-off-by: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
>>>> Or perhaps:
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
>>>> index 2b96f336589e..8d7b4eb5b5b9 100644
>>>> --- a/drivers/gpu/drm/i915/intel_sprite.c
>>>> +++ b/drivers/gpu/drm/i915/intel_sprite.c
>>>> @@ -747,7 +747,6 @@ intel_check_sprite_plane(struct drm_plane *plane,
>>>>           struct drm_framebuffer *fb = state->base.fb;
>>>>           int crtc_x, crtc_y;
>>>>           unsigned int crtc_w, crtc_h;
>>>> -       uint32_t src_x, src_y, src_w, src_h;
>>>>           struct drm_rect *src = &state->src;
>>>>           struct drm_rect *dst = &state->dst;
>>>>           const struct drm_rect *clip = &state->clip;
>>>> @@ -813,6 +812,8 @@ intel_check_sprite_plane(struct drm_plane *plane,
>>>>           crtc_h = drm_rect_height(dst);
>>>>    
>>>>           if (state->visible) {
>>>> +               u32 src_x, src_y, src_w, src_h;
>>>> +
>>>>                   /* check again in case clipping clamped the results */
>>>>                   hscale = drm_rect_calc_hscale(src, dst, min_scale, max_scale);
>>>>                   if (hscale < 0) {
>>>> @@ -871,10 +872,9 @@ intel_check_sprite_plane(struct drm_plane *plane,
>>>>                           if (crtc_w == 0)
>>>>                                   state->visible = false;
>>>>                   }
>>>> -       }
>>>>    
>>>>                   /* Check size restrictions when scaling */
>>>> -       if (state->visible && (src_w != crtc_w || src_h != crtc_h)) {
>>>> +               if (src_w != crtc_w || src_h != crtc_h) {
>>> That would change what it does.
>> yes, checked the code where inside each if condition loop we may be
>> changing the state->visible var itself. Next condition check it may be
>> false too.
>>
>> The place giving compiler error
>>                   src->x1 = src_x << 16;
>>                   src->x2 = (src_x + src_w) << 16;
>>                   src->y1 = src_y << 16;
>>                   src->y2 = (src_y + src_h) << 16;
>>
>> Then just one line change of initializing the variables is better?
> Or maybe fix your compiler instead? I don't get any warning/errors from
> this. What version of gcc are you using?
  I still get the warning and error if -Werror is enabled, And on 
Makefile O1 optimization is enabled. (note on Android build by default 
Werror is enabled and gcc-- GCC: (GNU) 4.9.2
)

on generic build, gcc --gcc (Ubuntu 4.9.3-5ubuntu1~14.04) 4.9.3

following are the error..
   CC      drivers/staging/android/timed_gpio.o
/home/nbikash/PROJ_CODEBASE/MDsrt_WW44.2/kernel/bxt/drivers/gpu/drm/i915/intel_sprite.c: 
In function 'intel_check_sprite_plane':
/home/nbikash/PROJ_CODEBASE/MDsrt_WW44.2/kernel/bxt/drivers/gpu/drm/i915/intel_sprite.c:1241:20: 
error: 'src_h' may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
    src->y2 = (src_y + src_h) << 16;
                     ^
/home/nbikash/PROJ_CODEBASE/MDsrt_WW44.2/kernel/bxt/drivers/gpu/drm/i915/intel_sprite.c:1239:20: 
error: 'src_w' may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
    src->x2 = (src_x + src_w) << 16;
                     ^
/home/nbikash/PROJ_CODEBASE/MDsrt_WW44.2/kernel/bxt/drivers/gpu/drm/i915/intel_sprite.c:1241:20: 
error: 'src_y' may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
    src->y2 = (src_y + src_h) << 16;
                     ^
/home/nbikash/PROJ_CODEBASE/MDsrt_WW44.2/kernel/bxt/drivers/gpu/drm/i915/intel_sprite.c:1238:19: 
error: 'src_x' may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
    src->x1 = src_x << 16;
>
>>>>                           unsigned int width_bytes;
>>>>    
>>>>                           WARN_ON(!can_scale);
>>>> @@ -898,7 +898,6 @@ intel_check_sprite_plane(struct drm_plane *plane,
>>>>                           }
>>>>                   }
>>>>    
>>>> -       if (state->visible) {
>>>>                   src->x1 = src_x << 16;
>>>>                   src->x2 = (src_x + src_w) << 16;
>>>>                   src->y1 = src_y << 16;
>>>>
>>>> And make both the compiler and reader happier
>>>> -Chris
>>>>
>>>> -- 
>>>> Chris Wilson, Intel Open Source Technology Centre
>>>> _______________________________________________
>>>> Intel-gfx mailing list
>>>> Intel-gfx@lists.freedesktop.org
>>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

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