[Intel-gfx] [PATCH 05/22] drm/radeon: Use drm_mode_copy()

Ville Syrjala ville.syrjala at linux.intel.com
Fri Feb 18 10:03:46 UTC 2022

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

struct drm_display_mode embeds a list head, so overwriting
the full struct with another one will corrupt the list
(if the destination mode is on a list). Use drm_mode_copy()
instead which explicitly preserves the list head of
the destination mode.

Even if we know the destination mode is not on any list
using drm_mode_copy() seems decent as it sets a good
example. Bad examples of not using it might eventually
get copied into code where preserving the list head
actually matters.

Obviously one case not covered here is when the mode
itself is embedded in a larger structure and the whole
structure is copied. But if we are careful when copying
into modes embedded in structures I think we can be a
little more reassured that bogus list heads haven't been
propagated in.


@depends on !is_mode_copy@
struct drm_display_mode *mode;
expression E, S;
- *mode = E
+ drm_mode_copy(mode, &E)
- memcpy(mode, E, S)
+ drm_mode_copy(mode, E)

@depends on !is_mode_copy@
struct drm_display_mode mode;
expression E;
- mode = E
+ drm_mode_copy(&mode, &E)
- memcpy(&mode, E, S)
+ drm_mode_copy(&mode, E)

struct drm_display_mode *mode;
- &*mode
+ mode

Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: amd-gfx at lists.freedesktop.org
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
 drivers/gpu/drm/radeon/radeon_connectors.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index a7925a8290b2..0cb1345c6ba4 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -777,7 +777,7 @@ static void radeon_fixup_lvds_native_mode(struct drm_encoder *encoder,
 		if (mode->type & DRM_MODE_TYPE_PREFERRED) {
 			if (mode->hdisplay != native_mode->hdisplay ||
 			    mode->vdisplay != native_mode->vdisplay)
-				memcpy(native_mode, mode, sizeof(*mode));
+				drm_mode_copy(native_mode, mode);
@@ -786,7 +786,7 @@ static void radeon_fixup_lvds_native_mode(struct drm_encoder *encoder,
 		list_for_each_entry_safe(mode, t, &connector->probed_modes, head) {
 			if (mode->hdisplay == native_mode->hdisplay &&
 			    mode->vdisplay == native_mode->vdisplay) {
-				*native_mode = *mode;
+				drm_mode_copy(native_mode, mode);
 				drm_mode_set_crtcinfo(native_mode, CRTC_INTERLACE_HALVE_V);
 				DRM_DEBUG_KMS("Determined LVDS native mode details from EDID\n");

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