drm: add helper functions to retrieve old and new crtc

Add new helper functions, drm_atomic_get_old_crtc_for_encoder
and drm_atomic_get_new_crtc_for_encoder to retrieve the
corresponding crtc for the encoder.

Signed-off-by: Sankeerth Billakanti <quic_sbillaka@quicinc.com>
Signed-off-by: Vinod Polimera <quic_vpolimer@quicinc.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Patchwork: https://patchwork.freedesktop.org/patch/524718/
Link: https://lore.kernel.org/r/1677774797-31063-2-git-send-email-quic_vpolimer@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/drm_atomic.c

@@ -984,6 +984,66 @@ drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
 }
 EXPORT_SYMBOL(drm_atomic_get_new_connector_for_encoder);
 
+/**
+ * drm_atomic_get_old_crtc_for_encoder - Get old crtc for an encoder
+ * @state: Atomic state
+ * @encoder: The encoder to fetch the crtc state for
+ *
+ * This function finds and returns the crtc that was connected to @encoder
+ * as specified by the @state.
+ *
+ * Returns: The old crtc connected to @encoder, or NULL if the encoder is
+ * not connected.
+ */
+struct drm_crtc *
+drm_atomic_get_old_crtc_for_encoder(struct drm_atomic_state *state,
+				    struct drm_encoder *encoder)
+{
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+
+	connector = drm_atomic_get_old_connector_for_encoder(state, encoder);
+	if (!connector)
+		return NULL;
+
+	conn_state = drm_atomic_get_old_connector_state(state, connector);
+	if (!conn_state)
+		return NULL;
+
+	return conn_state->crtc;
+}
+EXPORT_SYMBOL(drm_atomic_get_old_crtc_for_encoder);
+
+/**
+ * drm_atomic_get_new_crtc_for_encoder - Get new crtc for an encoder
+ * @state: Atomic state
+ * @encoder: The encoder to fetch the crtc state for
+ *
+ * This function finds and returns the crtc that will be connected to @encoder
+ * as specified by the @state.
+ *
+ * Returns: The new crtc connected to @encoder, or NULL if the encoder is
+ * not connected.
+ */
+struct drm_crtc *
+drm_atomic_get_new_crtc_for_encoder(struct drm_atomic_state *state,
+				    struct drm_encoder *encoder)
+{
+	struct drm_connector *connector;
+	struct drm_connector_state *conn_state;
+
+	connector = drm_atomic_get_new_connector_for_encoder(state, encoder);
+	if (!connector)
+		return NULL;
+
+	conn_state = drm_atomic_get_new_connector_state(state, connector);
+	if (!conn_state)
+		return NULL;
+
+	return conn_state->crtc;
+}
+EXPORT_SYMBOL(drm_atomic_get_new_crtc_for_encoder);
+
 /**
  * drm_atomic_get_connector_state - get connector state
  * @state: global atomic state object

include/drm/drm_atomic.h

@@ -528,6 +528,13 @@ struct drm_connector *
 drm_atomic_get_new_connector_for_encoder(const struct drm_atomic_state *state,
 					 struct drm_encoder *encoder);
 
+struct drm_crtc *
+drm_atomic_get_old_crtc_for_encoder(struct drm_atomic_state *state,
+					 struct drm_encoder *encoder);
+struct drm_crtc *
+drm_atomic_get_new_crtc_for_encoder(struct drm_atomic_state *state,
+					 struct drm_encoder *encoder);
+
 /**
  * drm_atomic_get_existing_crtc_state - get CRTC state, if it exists
  * @state: global atomic state object