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

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Date: Sun, 17 Mar 2024 18:27:53 -0300
From: Maíra Canal <mcanal@...lia.com>
To: Melissa Wen <mwen@...lia.com>, Arthur Grillo <arthurgrillo@...eup.net>
Cc: 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

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?

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>
>>