linux-kernel - [PATCH] drm: msm: avoid false-positive -Wmaybe-uninitialized warning

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Date:   Mon,  4 Dec 2017 15:44:23 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Rob Clark <robdclark@...il.com>, David Airlie <airlied@...ux.ie>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Archit Taneja <architt@...eaurora.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Liviu Dudau <Liviu.Dudau@....com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Gustavo Padovan <gustavo.padovan@...labora.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm: msm: avoid false-positive -Wmaybe-uninitialized warning

gcc-8 -fsanitize-coverage=trace-pc produces a false-positive warning:

drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c: In function 'mdp5_plane_mode_set.isra.8':
drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c:1053:3: error: 'crtc_x_r' may be used uninitialized in this function [-Werror=maybe-uninitialized]

It's relatively clear from reading the source that this cannot happen,
and older compilers get it right. This rearranges the code remove
the two affected variables, which reliably avoids the problem.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c
index be50445f9901..c50449882037 100644
--- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c
+++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_plane.c
@@ -964,8 +964,6 @@ static int mdp5_plane_mode_set(struct drm_plane *plane,
 	uint32_t src_x, src_y;
 	uint32_t src_w, src_h;
 	uint32_t src_img_w, src_img_h;
-	uint32_t src_x_r;
-	int crtc_x_r;
 	int ret;
 
 	nplanes = fb->format->num_planes;
@@ -1010,9 +1008,6 @@ static int mdp5_plane_mode_set(struct drm_plane *plane,
 		crtc_w /= 2;
 		src_w /= 2;
 		src_img_w /= 2;
-
-		crtc_x_r = crtc_x + crtc_w;
-		src_x_r = src_x + src_w;
 	}
 
 	ret = calc_scalex_steps(plane, pix_format, src_w, crtc_w, step.x);
@@ -1052,9 +1047,9 @@ static int mdp5_plane_mode_set(struct drm_plane *plane,
 	if (right_hwpipe)
 		mdp5_hwpipe_mode_set(mdp5_kms, right_hwpipe, fb, &step, &pe,
 				     config, hdecm, vdecm, hflip, vflip,
-				     crtc_x_r, crtc_y, crtc_w, crtc_h,
+				     crtc_x + crtc_w, crtc_y, crtc_w, crtc_h,
 				     src_img_w, src_img_h,
-				     src_x_r, src_y, src_w, src_h);
+				     src_x + src_w, src_y, src_w, src_h);
 
 	plane->fb = fb;
 
-- 
2.9.0