slimbus: Add SLIMbus bus type

SLIMbus (Serial Low Power Interchip Media Bus) is a specification
developed by MIPI (Mobile Industry Processor Interface) alliance.
SLIMbus is a 2-wire implementation, which is used to communicate with
peripheral components like audio-codec.
SLIMbus uses Time-Division-Multiplexing to accommodate multiple data
channels, and control channel. Control channel has messages to do
device-enumeration, messages to send/receive control-data to/from
SLIMbus devices, messages for port/channel management, and messages to
do bandwidth allocation.
The framework supports multiple instances of the bus (1 controller per
bus), and multiple slave devices per controller.

This patch adds support to basic silmbus core which includes support to
SLIMbus type, slimbus device registeration and some basic data structures.

Signed-off-by: Sagar Dharia <[email protected]>
Signed-off-by: Srinivas Kandagatla <[email protected]>
Reviwed-by: Mark Brown <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/slimbus/Kconfig

@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# SLIMbus driver configuration
+#
+menuconfig SLIMBUS
+	tristate "SLIMbus support"
+	help
+	  SLIMbus is standard interface between System-on-Chip and audio codec,
+	  and other peripheral components in typical embedded systems.
+
+	  If unsure, choose N.
+
+if SLIMBUS
+
+# SLIMbus controllers
+
+endif

drivers/slimbus/Makefile

@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for kernel SLIMbus framework.
+#
+obj-$(CONFIG_SLIMBUS)			+= slimbus.o
+slimbus-y				:= core.o

drivers/slimbus/core.c

@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2011-2017, The Linux Foundation
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/slimbus.h>
+
+static const struct slim_device_id *slim_match(const struct slim_device_id *id,
+					       const struct slim_device *sbdev)
+{
+	while (id->manf_id != 0 || id->prod_code != 0) {
+		if (id->manf_id == sbdev->e_addr.manf_id &&
+		    id->prod_code == sbdev->e_addr.prod_code)
+			return id;
+		id++;
+	}
+	return NULL;
+}
+
+static int slim_device_match(struct device *dev, struct device_driver *drv)
+{
+	struct slim_device *sbdev = to_slim_device(dev);
+	struct slim_driver *sbdrv = to_slim_driver(drv);
+
+	return !!slim_match(sbdrv->id_table, sbdev);
+}
+
+static int slim_device_probe(struct device *dev)
+{
+	struct slim_device	*sbdev = to_slim_device(dev);
+	struct slim_driver	*sbdrv = to_slim_driver(dev->driver);
+
+	return sbdrv->probe(sbdev);
+}
+
+static int slim_device_remove(struct device *dev)
+{
+	struct slim_device *sbdev = to_slim_device(dev);
+	struct slim_driver *sbdrv;
+
+	if (dev->driver) {
+		sbdrv = to_slim_driver(dev->driver);
+		if (sbdrv->remove)
+			sbdrv->remove(sbdev);
+	}
+
+	return 0;
+}
+
+struct bus_type slimbus_bus = {
+	.name		= "slimbus",
+	.match		= slim_device_match,
+	.probe		= slim_device_probe,
+	.remove		= slim_device_remove,
+};
+EXPORT_SYMBOL_GPL(slimbus_bus);
+
+/*
+ * __slim_driver_register() - Client driver registration with SLIMbus
+ *
+ * @drv:Client driver to be associated with client-device.
+ * @owner: owning module/driver
+ *
+ * This API will register the client driver with the SLIMbus
+ * It is called from the driver's module-init function.
+ */
+int __slim_driver_register(struct slim_driver *drv, struct module *owner)
+{
+	/* ID table and probe are mandatory */
+	if (!drv->id_table || !drv->probe)
+		return -EINVAL;
+
+	drv->driver.bus = &slimbus_bus;
+	drv->driver.owner = owner;
+
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(__slim_driver_register);
+
+/*
+ * slim_driver_unregister() - Undo effect of slim_driver_register
+ *
+ * @drv: Client driver to be unregistered
+ */
+void slim_driver_unregister(struct slim_driver *drv)
+{
+	driver_unregister(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(slim_driver_unregister);
+
+static void __exit slimbus_exit(void)
+{
+	bus_unregister(&slimbus_bus);
+}
+module_exit(slimbus_exit);
+
+static int __init slimbus_init(void)
+{
+	return bus_register(&slimbus_bus);
+}
+postcore_initcall(slimbus_init);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("SLIMbus core");