+
+/**
+ * drm_encoder_crtc_ok - can a given crtc drive a given encoder?
+ * @encoder: encoder to test
+ * @crtc: crtc to test
+ *
+ * Return false if @encoder can't be driven by @crtc, true otherwise.
+ */
+static bool drm_encoder_crtc_ok(struct drm_encoder *encoder,
+ struct drm_crtc *crtc)
+{
+ struct drm_device *dev;
+ struct drm_crtc *tmp;
+ int crtc_mask = 1;
+
+ WARN(!crtc, "checking null crtc?");
+
+ dev = crtc->dev;
+
+ list_for_each_entry(tmp, &dev->mode_config.crtc_list, head) {
+ if (tmp == crtc)
+ break;
+ crtc_mask <<= 1;
+ }
+
+ if (encoder->possible_crtcs & crtc_mask)
+ return true;
+ return false;
+}
+
+/*
+ * Check the CRTC we're going to map each output to vs. its current
+ * CRTC. If they don't match, we have to disable the output and the CRTC
+ * since the driver will have to re-route things.
+ */
+static void
+drm_crtc_prepare_encoders(struct drm_device *dev)
+{
+ struct drm_encoder_helper_funcs *encoder_funcs;
+ struct drm_encoder *encoder;
+
+ list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
+ encoder_funcs = encoder->helper_private;
+ /* Disable unused encoders */
+ if (encoder->crtc == NULL)
+ (*encoder_funcs->dpms)(encoder, DRM_MODE_DPMS_OFF);
+ /* Disable encoders whose CRTC is about to change */
+ if (encoder_funcs->get_crtc &&
+ encoder->crtc != (*encoder_funcs->get_crtc)(encoder))
+ (*encoder_funcs->dpms)(encoder, DRM_MODE_DPMS_OFF);
+ }
+}
+