[PATCH 19/22] drm/i915: Use drm_mode_copy()

[Ville Syrjala]

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.

@is_mode_copy@
@@
drm_mode_copy(...)
{
...
}

@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

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 74c5a99ab276..661e36435793 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -5506,8 +5506,10 @@ intel_crtc_copy_uapi_to_hw_state_modeset(struct intel_atomic_state *state,
 
 	crtc_state->hw.enable = crtc_state->uapi.enable;
 	crtc_state->hw.active = crtc_state->uapi.active;
-	crtc_state->hw.mode = crtc_state->uapi.mode;
-	crtc_state->hw.adjusted_mode = crtc_state->uapi.adjusted_mode;
+	drm_mode_copy(&crtc_state->hw.mode,
+		      &crtc_state->uapi.mode);
+	drm_mode_copy(&crtc_state->hw.adjusted_mode,
+		      &crtc_state->uapi.adjusted_mode);
 	crtc_state->hw.scaling_filter = crtc_state->uapi.scaling_filter;
 
 	intel_crtc_copy_uapi_to_hw_state_nomodeset(state, crtc);
@@ -5584,9 +5586,12 @@ copy_bigjoiner_crtc_state_modeset(struct intel_atomic_state *state,
 	memset(&slave_crtc_state->hw, 0, sizeof(slave_crtc_state->hw));
 	slave_crtc_state->hw.enable = master_crtc_state->hw.enable;
 	slave_crtc_state->hw.active = master_crtc_state->hw.active;
-	slave_crtc_state->hw.mode = master_crtc_state->hw.mode;
-	slave_crtc_state->hw.pipe_mode = master_crtc_state->hw.pipe_mode;
-	slave_crtc_state->hw.adjusted_mode = master_crtc_state->hw.adjusted_mode;
+	drm_mode_copy(&slave_crtc_state->hw.mode,
+		      &master_crtc_state->hw.mode);
+	drm_mode_copy(&slave_crtc_state->hw.pipe_mode,
+		      &master_crtc_state->hw.pipe_mode);
+	drm_mode_copy(&slave_crtc_state->hw.adjusted_mode,
+		      &master_crtc_state->hw.adjusted_mode);
 	slave_crtc_state->hw.scaling_filter = master_crtc_state->hw.scaling_filter;
 
 	copy_bigjoiner_crtc_state_nomodeset(state, slave_crtc);
-- 
2.34.1