[RFC PATCH v3 01/23] drm: Don't treat 0 as -1 in drm_fixp2int_ceil

[Melissa Wen]

On 12/06, Melissa Wen wrote:
> On 11/08, Harry Wentland wrote:
> > Unit testing this in VKMS shows that passing 0 into
> > this function returns -1, which is highly counter-
> > intuitive. Fix it by checking whether the input is
> > >= 0 instead of > 0.
> > 
> Nice finding. Thanks!
> 
> Could you add the fixes tag? AFAIU, this one:
> 
> Fixes: 64566b5e767f9 ("drm: Add drm_fixp_from_fraction and drm_fixp2int_ceil")
> Reviewed-by: Melissa Wen <mwen at igalia.com>

cc'ing msm people:

Hi,

Only msm and vkms currently use this function.

I see many points where msm resorts to a conditional that avoid passing
0 into this function. For example:

	if (temp2_fp)
		temp = drm_fixp2int_ceil(temp2_fp);
	else
		temp = 0;

Can someone from msm ack this patch too?

Thanks,

Melissa

> 
> > Signed-off-by: Harry Wentland <harry.wentland at amd.com>
> > Reviewed-by: Simon Ser <contact at emersion.fr>
> > ---
> >  include/drm/drm_fixed.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
> > index 6ea339d5de08..0c9f917a4d4b 100644
> > --- a/include/drm/drm_fixed.h
> > +++ b/include/drm/drm_fixed.h
> > @@ -95,7 +95,7 @@ static inline int drm_fixp2int_round(s64 a)
> >  
> >  static inline int drm_fixp2int_ceil(s64 a)
> >  {
> > -	if (a > 0)
> > +	if (a >= 0)
> >  		return drm_fixp2int(a + DRM_FIXED_ALMOST_ONE);
> >  	else
> >  		return drm_fixp2int(a - DRM_FIXED_ALMOST_ONE);
> > -- 
> > 2.42.1
> >