drm/i915: Use container_of_const() for states

commit 64f6a5d192 ("container_of: add container_of_const()
that preserves const-ness of the pointer") is nice. Let's use
it so that we don't accidentally cast away the const from our
state pointers.

The only thing I don't particularly like about container_of_const()
is that it still accepts void* in addition to the proper pointer
types, but that's how most other things in C work anyway so I
guess we can live with it.

And while at it rename the macro arguments to be a bit more
descriptive than just 'x'.

TODO: maybe convert *all* container_of() uses to container_of_const()?

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240307151810.24208-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/display/intel_bw.h

@@ -52,7 +52,8 @@ struct intel_bw_state {
 	u8 num_active_planes[I915_MAX_PIPES];
 };
 
-#define to_intel_bw_state(x) container_of((x), struct intel_bw_state, base)
+#define to_intel_bw_state(global_state) \
+	container_of_const((global_state), struct intel_bw_state, base)
 
 struct intel_bw_state *
 intel_atomic_get_old_bw_state(struct intel_atomic_state *state);

drivers/gpu/drm/i915/display/intel_cdclk.h

@@ -80,7 +80,9 @@ int intel_cdclk_state_set_joined_mbus(struct intel_atomic_state *state, bool joi
 struct intel_cdclk_state *
 intel_atomic_get_cdclk_state(struct intel_atomic_state *state);
 
-#define to_intel_cdclk_state(x) container_of((x), struct intel_cdclk_state, base)
+#define to_intel_cdclk_state(global_state) \
+	container_of_const((global_state), struct intel_cdclk_state, base)
+
 #define intel_atomic_get_old_cdclk_state(state) \
 	to_intel_cdclk_state(intel_atomic_get_old_global_obj_state(state, &to_i915(state->base.dev)->display.cdclk.obj))
 #define intel_atomic_get_new_cdclk_state(state) \

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -661,7 +661,8 @@ struct intel_digital_connector_state {
 	int broadcast_rgb;
 };
 
-#define to_intel_digital_connector_state(x) container_of(x, struct intel_digital_connector_state, base)
+#define to_intel_digital_connector_state(conn_state) \
+	container_of_const((conn_state), struct intel_digital_connector_state, base)
 
 struct dpll {
 	/* given values */
@@ -1617,12 +1618,17 @@ struct intel_watermark_params {
 
 #define to_intel_atomic_state(x) container_of(x, struct intel_atomic_state, base)
 #define to_intel_crtc(x) container_of(x, struct intel_crtc, base)
-#define to_intel_crtc_state(x) container_of(x, struct intel_crtc_state, uapi)
 #define to_intel_connector(x) container_of(x, struct intel_connector, base)
 #define to_intel_encoder(x) container_of(x, struct intel_encoder, base)
-#define to_intel_framebuffer(x) container_of(x, struct intel_framebuffer, base)
 #define to_intel_plane(x) container_of(x, struct intel_plane, base)
-#define to_intel_plane_state(x) container_of(x, struct intel_plane_state, uapi)
+
+#define to_intel_crtc_state(crtc_state) \
+	container_of_const((crtc_state), struct intel_crtc_state, uapi)
+#define to_intel_plane_state(plane_state) \
+	container_of_const((plane_state), struct intel_plane_state, uapi)
+#define to_intel_framebuffer(fb) \
+	container_of_const((fb), struct intel_framebuffer, base)
+
 #define intel_fb_obj(x) ((x) ? to_intel_bo((x)->obj[0]) : NULL)
 
 struct intel_hdmi {

drivers/gpu/drm/i915/display/intel_pmdemand.h

@@ -43,9 +43,8 @@ struct intel_pmdemand_state {
 	struct pmdemand_params params;
 };
 
-#define to_intel_pmdemand_state(x) container_of((x), \
-						struct intel_pmdemand_state, \
-						base)
+#define to_intel_pmdemand_state(global_state) \
+	container_of_const((global_state), struct intel_pmdemand_state, base)
 
 void intel_pmdemand_init_early(struct drm_i915_private *i915);
 int intel_pmdemand_init(struct drm_i915_private *i915);

drivers/gpu/drm/i915/display/intel_sdvo.c

@@ -193,7 +193,7 @@ to_intel_sdvo_connector(struct drm_connector *connector)
 }
 
 #define to_intel_sdvo_connector_state(conn_state) \
-	container_of((conn_state), struct intel_sdvo_connector_state, base.base)
+	container_of_const((conn_state), struct intel_sdvo_connector_state, base.base)
 
 static bool
 intel_sdvo_output_setup(struct intel_sdvo *intel_sdvo);

drivers/gpu/drm/i915/display/intel_tv.c

@@ -885,7 +885,8 @@ struct intel_tv_connector_state {
 	bool bypass_vfilter;
 };
 
-#define to_intel_tv_connector_state(x) container_of(x, struct intel_tv_connector_state, base)
+#define to_intel_tv_connector_state(conn_state) \
+	container_of_const((conn_state), struct intel_tv_connector_state, base)
 
 static struct drm_connector_state *
 intel_tv_connector_duplicate_state(struct drm_connector *connector)

drivers/gpu/drm/i915/display/skl_watermark.h

@@ -65,7 +65,9 @@ struct intel_dbuf_state {
 struct intel_dbuf_state *
 intel_atomic_get_dbuf_state(struct intel_atomic_state *state);
 
-#define to_intel_dbuf_state(x) container_of((x), struct intel_dbuf_state, base)
+#define to_intel_dbuf_state(global_state) \
+	container_of_const((global_state), struct intel_dbuf_state, base)
+
 #define intel_atomic_get_old_dbuf_state(state) \
 	to_intel_dbuf_state(intel_atomic_get_old_global_obj_state(state, &to_i915(state->base.dev)->display.dbuf.obj))
 #define intel_atomic_get_new_dbuf_state(state) \