linux-kernel - [PATCH] drm/rockchip: vop2: fix uninitialized variable possible

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Date:   Thu, 16 Mar 2023 09:23:02 -0400
From:   Tom Rix <trix@...hat.com>
To:     hjc@...k-chips.com, heiko@...ech.de, airlied@...il.com,
        daniel@...ll.ch, nathan@...nel.org, ndesaulniers@...gle.com,
        michael.riesch@...fvision.net, s.hauer@...gutronix.de
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Tom Rix <trix@...hat.com>
Subject: [PATCH] drm/rockchip: vop2: fix uninitialized variable possible_crtcs

clang reportes this error
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2322:8: error:
  variable 'possible_crtcs' is used uninitialized whenever 'if'
  condition is false [-Werror,-Wsometimes-uninitialized]
                        if (vp) {
                            ^~
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2336:36: note:
  uninitialized use occurs here
                ret = vop2_plane_init(vop2, win, possible_crtcs);
                                                 ^~~~~~~~~~~~~~
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2322:4:
  note: remove the 'if' if its condition is always true
                        if (vp) {
                        ^~~~~~~~

The else-statement changes the win->type to OVERLAY without setting the
possible_crtcs variable.  Rework the block, initialize possible_crtcs to
0 to remove the else-statement.  Split the else-if-statement out to its
own if-statement so the OVERLAY check will catch when the win-type has
been changed.

Fixes: 368419a2d429 ("drm/rockchip: vop2: initialize possible_crtcs properly")
Signed-off-by: Tom Rix <trix@...hat.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index 03ca32cd2050..fce992c3506f 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
@@ -2301,7 +2301,7 @@ static int vop2_create_crtcs(struct vop2 *vop2)
 	nvp = 0;
 	for (i = 0; i < vop2->registered_num_wins; i++) {
 		struct vop2_win *win = &vop2->win[i];
-		u32 possible_crtcs;
+		u32 possible_crtcs = 0;
 
 		if (vop2->data->soc_id == 3566) {
 			/*
@@ -2327,12 +2327,11 @@ static int vop2_create_crtcs(struct vop2 *vop2)
 				/* change the unused primary window to overlay window */
 				win->type = DRM_PLANE_TYPE_OVERLAY;
 			}
-		} else if (win->type == DRM_PLANE_TYPE_OVERLAY) {
-			possible_crtcs = (1 << nvps) - 1;
-		} else {
-			possible_crtcs = 0;
 		}
 
+		if (win->type == DRM_PLANE_TYPE_OVERLAY)
+			possible_crtcs = (1 << nvps) - 1;
+
 		ret = vop2_plane_init(vop2, win, possible_crtcs);
 		if (ret) {
 			drm_err(vop2->drm, "failed to init plane %s: %d\n",
-- 
2.27.0