drm/probe-helper: add drm_connector_helper_get_modes()

Add a helper function to be used as the "default" .get_modes()
hook. This also works as an example of what the driver .get_modes()
hooks are supposed to do regarding the new drm_edid_read*() and
drm_edid_connector_update() calls.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/d985449ed4b95971490ab7c09d2d59b58a892769.1656494768.git.jani.nikula@intel.com

drivers/gpu/drm/drm_probe_helper.c

@@ -1049,3 +1049,37 @@ int drm_connector_helper_get_modes_from_ddc(struct drm_connector *connector)
 	return count;
 }
 EXPORT_SYMBOL(drm_connector_helper_get_modes_from_ddc);
+
+/**
+ * drm_connector_helper_get_modes - Read EDID and update connector.
+ * @connector: The connector
+ *
+ * Read the EDID using drm_edid_read() (which requires that connector->ddc is
+ * set), and update the connector using the EDID.
+ *
+ * This can be used as the "default" connector helper .get_modes() hook if the
+ * driver does not need any special processing. This is sets the example what
+ * custom .get_modes() hooks should do regarding EDID read and connector update.
+ *
+ * Returns: Number of modes.
+ */
+int drm_connector_helper_get_modes(struct drm_connector *connector)
+{
+	const struct drm_edid *drm_edid;
+	int count;
+
+	drm_edid = drm_edid_read(connector);
+
+	/*
+	 * Unconditionally update the connector. If the EDID was read
+	 * successfully, fill in the connector information derived from the
+	 * EDID. Otherwise, if the EDID is NULL, clear the connector
+	 * information.
+	 */
+	count = drm_edid_connector_update(connector, drm_edid);
+
+	drm_edid_free(drm_edid);
+
+	return count;
+}
+EXPORT_SYMBOL(drm_connector_helper_get_modes);

include/drm/drm_probe_helper.h

@@ -27,5 +27,6 @@ void drm_kms_helper_poll_enable(struct drm_device *dev);
 bool drm_kms_helper_is_poll_worker(void);
 
 int drm_connector_helper_get_modes_from_ddc(struct drm_connector *connector);
+int drm_connector_helper_get_modes(struct drm_connector *connector);
 
 #endif