drm/atomic-helper: Add an analog TV atomic_check implementation

The analog TV connector drivers share some atomic_check logic, and the new
TV standard property have created some boilerplate that can be shared
across drivers too.

Let's create an atomic_check helper for those use cases.
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Acked-in-principle-or-something-like-that-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://lore.kernel.org/r/20220728-rpi-analog-tv-properties-v10-14-256dad125326@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/drm_atomic_state_helper.c

@@ -556,6 +556,55 @@ void drm_atomic_helper_connector_tv_reset(struct drm_connector *connector)
 }
 EXPORT_SYMBOL(drm_atomic_helper_connector_tv_reset);
 
+/**
+ * @drm_atomic_helper_connector_tv_check: Validate an analog TV connector state
+ * @connector: DRM Connector
+ * @state: the DRM State object
+ *
+ * Checks the state object to see if the requested state is valid for an
+ * analog TV connector.
+ *
+ * Returns:
+ * Zero for success, a negative error code on error.
+ */
+int drm_atomic_helper_connector_tv_check(struct drm_connector *connector,
+					 struct drm_atomic_state *state)
+{
+	struct drm_connector_state *old_conn_state =
+		drm_atomic_get_old_connector_state(state, connector);
+	struct drm_connector_state *new_conn_state =
+		drm_atomic_get_new_connector_state(state, connector);
+	struct drm_crtc_state *crtc_state;
+	struct drm_crtc *crtc;
+
+	crtc = new_conn_state->crtc;
+	if (!crtc)
+		return 0;
+
+	crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+	if (!crtc_state)
+		return -EINVAL;
+
+	if (old_conn_state->tv.mode != new_conn_state->tv.mode)
+		crtc_state->mode_changed = true;
+
+	if (old_conn_state->tv.margins.left != new_conn_state->tv.margins.left ||
+	    old_conn_state->tv.margins.right != new_conn_state->tv.margins.right ||
+	    old_conn_state->tv.margins.top != new_conn_state->tv.margins.top ||
+	    old_conn_state->tv.margins.bottom != new_conn_state->tv.margins.bottom ||
+	    old_conn_state->tv.mode != new_conn_state->tv.mode ||
+	    old_conn_state->tv.brightness != new_conn_state->tv.brightness ||
+	    old_conn_state->tv.contrast != new_conn_state->tv.contrast ||
+	    old_conn_state->tv.flicker_reduction != new_conn_state->tv.flicker_reduction ||
+	    old_conn_state->tv.overscan != new_conn_state->tv.overscan ||
+	    old_conn_state->tv.saturation != new_conn_state->tv.saturation ||
+	    old_conn_state->tv.hue != new_conn_state->tv.hue)
+		crtc_state->connectors_changed = true;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_helper_connector_tv_check);
+
 /**
  * __drm_atomic_helper_connector_duplicate_state - copy atomic connector state
  * @connector: connector object

include/drm/drm_atomic_state_helper.h

@@ -26,6 +26,7 @@
 
 #include <linux/types.h>
 
+struct drm_atomic_state;
 struct drm_bridge;
 struct drm_bridge_state;
 struct drm_crtc;
@@ -71,6 +72,8 @@ void __drm_atomic_helper_connector_reset(struct drm_connector *connector,
 					 struct drm_connector_state *conn_state);
 void drm_atomic_helper_connector_reset(struct drm_connector *connector);
 void drm_atomic_helper_connector_tv_reset(struct drm_connector *connector);
+int drm_atomic_helper_connector_tv_check(struct drm_connector *connector,
+					 struct drm_atomic_state *state);
 void drm_atomic_helper_connector_tv_margins_reset(struct drm_connector *connector);
 void
 __drm_atomic_helper_connector_duplicate_state(struct drm_connector *connector,