linux-kernel - [PATCH 5.10 119/238] drm: Don't treat 0 as -1 in drm_fixp2int

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Date: Sun, 24 Mar 2024 19:38:27 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Harry Wentland <harry.wentland@....com>,
	Simon Ser <contact@...rsion.fr>,
	Melissa Wen <mwen@...lia.com>,
	Melissa Wen <melissa.srw@...il.com>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 119/238] drm: Don't treat 0 as -1 in drm_fixp2int_ceil

From: Harry Wentland <harry.wentland@....com>

[ Upstream commit cf8837d7204481026335461629b84ac7f4538fa5 ]

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.

Fixes: 64566b5e767f ("drm: Add drm_fixp_from_fraction and drm_fixp2int_ceil")
Signed-off-by: Harry Wentland <harry.wentland@....com>
Reviewed-by: Simon Ser <contact@...rsion.fr>
Reviewed-by: Melissa Wen <mwen@...lia.com>
Signed-off-by: Melissa Wen <melissa.srw@...il.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231108163647.106853-2-harry.wentland@amd.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 553210c02ee0f..627efa56e59fb 100644
--- a/include/drm/drm_fixed.h
+++ b/include/drm/drm_fixed.h
@@ -88,7 +88,7 @@ static inline int drm_fixp2int(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);
-- 
2.43.0