greybus: introduce a connection abstraction

Within a UniPro network a pair of CPorts can be linked to form a
UniPro Connection.  This patch creates a new abstraction to
represent an AP CPort that is connected with a CPort used by a
function within a Greybus module.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/Makefile

@@ -6,6 +6,7 @@ greybus-y :=	core.o		\
 		module.o	\
 		interface.o	\
 		function.o	\
+		connection.o	\
 		i2c-gb.o	\
 		gpio-gb.o	\
 		sdio-gb.o	\

drivers/staging/greybus/connection.c

+/*
+ * Greybus connections
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * Released under the GPLv2 only.
+ */
+
+#include "greybus.h"
+
+/*
+ * Set up a Greybus connection, representing the bidirectional link
+ * between a CPort on a (local) Greybus host device and a CPort on
+ * another Greybus module.
+ *
+ * Returns a pointer to the new connection if successful, or a null
+ * pointer otherwise.
+ */
+struct gb_connection *gb_connection_create(struct greybus_host_device *hd,
+				u16 cport_id, struct gb_function *function)
+{
+	struct gb_connection *connection;
+
+	connection = kzalloc(sizeof(*connection), GFP_KERNEL);
+	if (!connection)
+		return NULL;
+
+	connection->hd = hd;			/* XXX refcount? */
+	connection->cport_id = cport_id;
+	connection->function = function;	/* XXX refcount? */
+
+	return connection;
+}
+
+/*
+ * Tear down a previously set up connection.
+ */
+void gb_connection_destroy(struct gb_connection *connection)
+{
+	if (WARN_ON(!connection))
+		return;
+
+	/* XXX Need to wait for any outstanding requests to complete */
+
+	/* kref_put(function); */
+	/* kref_put(hd); */
+	kfree(connection);
+}

drivers/staging/greybus/connection.h

+/*
+ * Greybus connections
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * Released under the GPLv2 only.
+ */
+
+#ifndef __CONNECTION_H
+#define __CONNECTION_H
+
+#include <linux/list.h>
+
+#include "greybus.h"
+#include "function.h"
+
+struct gb_connection {
+	struct gb_function		*function;
+	struct greybus_host_device	*hd;
+	u16				cport_id;	/* Host side */
+
+	struct list_head		host_links;
+};
+
+bool gb_connection_setup(struct greybus_host_device *hd, u16 cport_id,
+				struct gb_function *function);
+void gb_connection_teardown(struct gb_connection *connection);
+
+#endif /* __CONNECTION_H */

drivers/staging/greybus/core.c

@@ -147,12 +147,22 @@ static struct device_type greybus_module_type = {
 	.release =	greybus_module_release,
 };
 
+/* XXX
+ * This needs to be driven by the list of functions that the
+ * manifest says are present.
+ */
 static int gb_init_subdevs(struct gb_module *gmod,
 			   const struct greybus_module_id *id)
 {
 	int retval;
 
 	/* Allocate all of the different "sub device types" for this device */
+
+	/* XXX
+	 * Decide what exactly we should get supplied for the i2c
+	 * probe, and then work that back to what should be present
+	 * in the manifest.
+	 */
 	retval = gb_i2c_probe(gmod, id);
 	if (retval)
 		goto error_i2c;

drivers/staging/greybus/greybus.h

@@ -23,6 +23,7 @@
 #include "module.h"
 #include "interface.h"
 #include "function.h"
+#include "connection.h"
 
 
 /* Matches up with the Greybus Protocol specification document */
@@ -180,6 +181,7 @@ struct greybus_host_device {
 	const struct greybus_host_driver *driver;
 
 	struct list_head modules;
+	struct list_head connections;
 
 	/* Private data for the host driver */
 	unsigned long hd_priv[0] __attribute__ ((aligned(sizeof(s64))));