drm: Look for an alias for the displays to use as the DRM device name

Allow DT aliases of eg DSI2 to force make DRM allocate the
display with the requested name.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

drivers/gpu/drm/drm_connector.c

@@ -34,6 +34,7 @@
 #include <drm/drm_utils.h>
 
 #include <linux/export.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/uaccess.h>
@@ -85,6 +86,7 @@ struct drm_conn_prop_enum_list {
 	int type;
 	const char *name;
 	struct ida ida;
+	int first_dyn_num;
 };
 
 /*
@@ -114,12 +116,41 @@ static struct drm_conn_prop_enum_list drm_connector_enum_list[] = {
 	{ DRM_MODE_CONNECTOR_USB, "USB" },
 };
 
+#define MAX_DT_NODE_NAME_LEN	20
+#define DT_DRM_NODE_PREFIX	"drm-"
+
+static void drm_connector_get_of_name(int type, char *node_name, int length)
+{
+	int i = 0;
+
+	strscpy(node_name, DT_DRM_NODE_PREFIX, length);
+
+	do {
+		node_name[i + strlen(DT_DRM_NODE_PREFIX)] =
+				tolower(drm_connector_enum_list[type].name[i]);
+
+	} while (drm_connector_enum_list[type].name[i++] &&
+		 i < length);
+
+	node_name[length - 1] = '\0';
+}
+
 void drm_connector_ida_init(void)
 {
-	int i;
+	int i, id;
+	char node_name[MAX_DT_NODE_NAME_LEN];
 
-	for (i = 0; i < ARRAY_SIZE(drm_connector_enum_list); i++)
+	for (i = 0; i < ARRAY_SIZE(drm_connector_enum_list); i++) {
 		ida_init(&drm_connector_enum_list[i].ida);
+
+		drm_connector_get_of_name(i, node_name, MAX_DT_NODE_NAME_LEN);
+
+		id = of_alias_get_highest_id(node_name);
+		if (id > 0)
+			drm_connector_enum_list[i].first_dyn_num = id + 1;
+		else
+			drm_connector_enum_list[i].first_dyn_num = 1;
+	}
 }
 
 void drm_connector_ida_destroy(void)
@@ -227,7 +258,9 @@ static int drm_connector_init_only(struct drm_device *dev,
 				   struct i2c_adapter *ddc)
 {
 	struct drm_mode_config *config = &dev->mode_config;
+	char node_name[MAX_DT_NODE_NAME_LEN];
 	int ret;
+	int id;
 	struct ida *connector_ida =
 		&drm_connector_enum_list[connector_type].ida;
 
@@ -257,8 +290,28 @@ static int drm_connector_init_only(struct drm_device *dev,
 	ret = 0;
 
 	connector->connector_type = connector_type;
-	connector->connector_type_id =
-		ida_alloc_min(connector_ida, 1, GFP_KERNEL);
+	connector->connector_type_id = 0;
+
+	drm_connector_get_of_name(connector_type, node_name, MAX_DT_NODE_NAME_LEN);
+	id = of_alias_get_id(dev->dev->of_node, node_name);
+	if (id > 0) {
+		/* Try and allocate the requested ID
+		 * Valid range is 1 to 31, hence ignoring 0 as an error
+		 */
+		int type_id = ida_alloc_range(connector_ida, id, id, GFP_KERNEL);
+
+		if (type_id > 0)
+			connector->connector_type_id = type_id;
+		else
+			drm_err(dev, "Failed to acquire type ID %d for interface type %s, ret %d\n",
+				id, drm_connector_enum_list[connector_type].name,
+				type_id);
+	}
+	if (!connector->connector_type_id)
+		connector->connector_type_id =
+				ida_alloc_min(connector_ida,
+					      drm_connector_enum_list[connector_type].first_dyn_num,
+					      GFP_KERNEL);
 	if (connector->connector_type_id < 0) {
 		ret = connector->connector_type_id;
 		goto out_put_id;