linux-kernel - Re: [PATCH v2] drm: Fix drm_fixp2int

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Date: Tue, 19 Mar 2024 11:24:05 -0300
From: Melissa Wen <mwen@...lia.com>
To: Maíra Canal <mcanal@...lia.com>
Cc: Arthur Grillo <arthurgrillo@...eup.net>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Pekka Paalanen <pekka.paalanen@...labora.com>, 
	Harry Wentland <harry.wentland@....com>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm: Fix drm_fixp2int_round() making it add 0.5

On 03/17, Maíra Canal wrote:
> Hi Melissa,
> 
> On 3/17/24 14:50, Melissa Wen wrote:
> > On 03/16, Arthur Grillo wrote:
> > > As well noted by Pekka[1], the rounding of drm_fixp2int_round is wrong.
> > > To round a number, you need to add 0.5 to the number and floor that,
> > > drm_fixp2int_round() is adding 0.0000076. Make it add 0.5.
> > > 
> > > [1]: https://lore.kernel.org/all/20240301135327.22efe0dd.pekka.paalanen@collabora.com/
> > > 
> > > Fixes: 8b25320887d7 ("drm: Add fixed-point helper to get rounded integer values")
> > > Suggested-by: Pekka Paalanen <pekka.paalanen@...labora.com>
> > > Reviewed-by: Harry Wentland <harry.wentland@....com>
> > > Signed-off-by: Arthur Grillo <arthurgrillo@...eup.net>
> > 
> > Great, thanks!
> > 
> > Reviewed-by: Melissa Wen <mwen@...lia.com>
> > 
> > I'll apply to drm-misc-next.
> 
> Shouldn't this patch be applied in drm-misc-fixes?

After discussions on IRC, I applied to drm-misc-next-fixes, since we are
in a merge window.

Thanks,

Melissa

> 
> Best Regards,
> - Maíra
> 
> > 
> > Melissa
> > 
> > > ---
> > > Changes in v2:
> > > - Add Fixes tag (Melissa Wen)
> > > - Remove DRM_FIXED_POINT_HALF (Melissa Wen)
> > > - Link to v1: https://lore.kernel.org/all/20240306-louis-vkms-conv-v1-1-5bfe7d129fdd@riseup.net/
> > > ---
> > >   include/drm/drm_fixed.h | 3 +--
> > >   1 file changed, 1 insertion(+), 2 deletions(-)
> > > 
> > > diff --git a/include/drm/drm_fixed.h b/include/drm/drm_fixed.h
> > > index 0c9f917a4d4b..81572d32db0c 100644
> > > --- a/include/drm/drm_fixed.h
> > > +++ b/include/drm/drm_fixed.h
> > > @@ -71,7 +71,6 @@ static inline u32 dfixed_div(fixed20_12 A, fixed20_12 B)
> > >   }
> > >   #define DRM_FIXED_POINT		32
> > > -#define DRM_FIXED_POINT_HALF	16
> > >   #define DRM_FIXED_ONE		(1ULL << DRM_FIXED_POINT)
> > >   #define DRM_FIXED_DECIMAL_MASK	(DRM_FIXED_ONE - 1)
> > >   #define DRM_FIXED_DIGITS_MASK	(~DRM_FIXED_DECIMAL_MASK)
> > > @@ -90,7 +89,7 @@ static inline int drm_fixp2int(s64 a)
> > >   static inline int drm_fixp2int_round(s64 a)
> > >   {
> > > -	return drm_fixp2int(a + (1 << (DRM_FIXED_POINT_HALF - 1)));
> > > +	return drm_fixp2int(a + DRM_FIXED_ONE / 2);
> > >   }
> > >   static inline int drm_fixp2int_ceil(s64 a)
> > > 
> > > ---
> > > base-commit: f89632a9e5fa6c4787c14458cd42a9ef42025434
> > > change-id: 20240315-drm_fixed-c680ba078ecb
> > > 
> > > Best regards,
> > > -- 
> > > Arthur Grillo <arthurgrillo@...eup.net>
> > >