linux-kernel - [PATCH v2] drm/armada: Fix off-by-one error in armada_overlay_get

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Message-Id: <7fbfcf4f1adafbe45e98257a07ac607718fe2aae.1679326886.git.geert+renesas@glider.be>
Date:   Mon, 20 Mar 2023 16:43:22 +0100
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Russell King <linux@...linux.org.uk>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Russell King <rmk+kernel@...linux.org.uk>
Subject: [PATCH v2] drm/armada: Fix off-by-one error in armada_overlay_get_property()

As ffs() returns one more than the index of the first bit set (zero
means no bits set), the color key mode value is shifted one position too
much.

Fix this by using FIELD_GET() instead.

Fixes: c96103b6c49ff9a8 ("drm/armada: move colorkey properties into overlay plane state")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
Compile-tested only.

v2:
  - Add Reviewed-by.
---
 drivers/gpu/drm/armada/armada_overlay.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/armada/armada_overlay.c b/drivers/gpu/drm/armada/armada_overlay.c
index f21eb8fb76d87285..3b9bd8ecda137f6d 100644
--- a/drivers/gpu/drm/armada/armada_overlay.c
+++ b/drivers/gpu/drm/armada/armada_overlay.c
@@ -4,6 +4,8 @@
  *  Rewritten from the dovefb driver, and Armada510 manuals.
  */
 
+#include <linux/bitfield.h>
+
 #include <drm/armada_drm.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
@@ -445,8 +447,8 @@ static int armada_overlay_get_property(struct drm_plane *plane,
 			     drm_to_overlay_state(state)->colorkey_ug,
 			     drm_to_overlay_state(state)->colorkey_vb, 0);
 	} else if (property == priv->colorkey_mode_prop) {
-		*val = (drm_to_overlay_state(state)->colorkey_mode &
-			CFG_CKMODE_MASK) >> ffs(CFG_CKMODE_MASK);
+		*val = FIELD_GET(CFG_CKMODE_MASK,
+				 drm_to_overlay_state(state)->colorkey_mode);
 	} else if (property == priv->brightness_prop) {
 		*val = drm_to_overlay_state(state)->brightness + 256;
 	} else if (property == priv->contrast_prop) {
-- 
2.34.1