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

Ville Syrjälä
2015-11-18T17:27:13Z

On Wed, Nov 18, 2015 at 10:33:55PM +0530, Maiti, Nabendu Bikash wrote:
>
>
> 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.

And why exactly are you building with -O1?

> (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

--
Ville Syrjälä
Intel OTC