drm/bridge: add ->edid_read hook and drm_bridge_edid_read()

Add new struct drm_edid based ->edid_read hook and
drm_bridge_edid_read() function to call the hook.

v2: Include drm/drm_edid.h
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/9d08d22eaffcb9c59a2b677e45d7e61fc689bc2f.1706038510.git.jani.nikula@intel.com

drivers/gpu/drm/drm_bridge.c

@@ -27,8 +27,9 @@
 #include <linux/mutex.h>
 
 #include <drm/drm_atomic_state_helper.h>
-#include <drm/drm_debugfs.h>
 #include <drm/drm_bridge.h>
+#include <drm/drm_debugfs.h>
+#include <drm/drm_edid.h>
 #include <drm/drm_encoder.h>
 #include <drm/drm_file.h>
 #include <drm/drm_of.h>
@@ -1206,6 +1207,47 @@ int drm_bridge_get_modes(struct drm_bridge *bridge,
 }
 EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
 
+/**
+ * drm_bridge_edid_read - read the EDID data of the connected display
+ * @bridge: bridge control structure
+ * @connector: the connector to read EDID for
+ *
+ * If the bridge supports output EDID retrieval, as reported by the
+ * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.edid_read to get
+ * the EDID and return it. Otherwise return NULL.
+ *
+ * If &drm_bridge_funcs.edid_read is not set, fall back to using
+ * drm_bridge_get_edid() and wrapping it in struct drm_edid.
+ *
+ * RETURNS:
+ * The retrieved EDID on success, or NULL otherwise.
+ */
+const struct drm_edid *drm_bridge_edid_read(struct drm_bridge *bridge,
+					    struct drm_connector *connector)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
+		return NULL;
+
+	/* Transitional: Fall back to ->get_edid. */
+	if (!bridge->funcs->edid_read) {
+		const struct drm_edid *drm_edid;
+		struct edid *edid;
+
+		edid = drm_bridge_get_edid(bridge, connector);
+		if (!edid)
+			return NULL;
+
+		drm_edid = drm_edid_alloc(edid, (edid->extensions + 1) * EDID_LENGTH);
+
+		kfree(edid);
+
+		return drm_edid;
+	}
+
+	return bridge->funcs->edid_read(bridge, connector);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_edid_read);
+
 /**
  * drm_bridge_get_edid - get the EDID data of the connected display
  * @bridge: bridge control structure
@@ -1215,6 +1257,8 @@ EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
  * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
  * get the EDID and return it. Otherwise return NULL.
  *
+ * Deprecated. Prefer using drm_bridge_edid_read().
+ *
  * RETURNS:
  * The retrieved EDID on success, or NULL otherwise.
  */

include/drm/drm_bridge.h

@@ -557,6 +557,37 @@ struct drm_bridge_funcs {
 	int (*get_modes)(struct drm_bridge *bridge,
 			 struct drm_connector *connector);
 
+	/**
+	 * @edid_read:
+	 *
+	 * Read the EDID data of the connected display.
+	 *
+	 * The @edid_read callback is the preferred way of reporting mode
+	 * information for a display connected to the bridge output. Bridges
+	 * that support reading EDID shall implement this callback and leave
+	 * the @get_modes callback unimplemented.
+	 *
+	 * The caller of this operation shall first verify the output
+	 * connection status and refrain from reading EDID from a disconnected
+	 * output.
+	 *
+	 * This callback is optional. Bridges that implement it shall set the
+	 * DRM_BRIDGE_OP_EDID flag in their &drm_bridge->ops.
+	 *
+	 * The connector parameter shall be used for the sole purpose of EDID
+	 * retrieval, and shall not be stored internally by bridge drivers for
+	 * future usage.
+	 *
+	 * RETURNS:
+	 *
+	 * An edid structure newly allocated with drm_edid_alloc() or returned
+	 * from drm_edid_read() family of functions on success, or NULL
+	 * otherwise. The caller is responsible for freeing the returned edid
+	 * structure with drm_edid_free().
+	 */
+	const struct drm_edid *(*edid_read)(struct drm_bridge *bridge,
+					    struct drm_connector *connector);
+
 	/**
 	 * @get_edid:
 	 *
@@ -888,6 +919,8 @@ drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
 enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge);
 int drm_bridge_get_modes(struct drm_bridge *bridge,
 			 struct drm_connector *connector);
+const struct drm_edid *drm_bridge_edid_read(struct drm_bridge *bridge,
+					    struct drm_connector *connector);
 struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
 				 struct drm_connector *connector);
 void drm_bridge_hpd_enable(struct drm_bridge *bridge,