usbip: vudc: Add VUDC main file

Add main vudc module file. This allows us to register suitable
platform device and driver (just like dummy_hcd does).

Currently number of vudc instances is determined using module
parameter but whole infrastructure is suitable to make vudc
creation dynamic (for example via configfs).

This commit is a result of cooperation between Samsung R&D Institute
Poland and Open Operating Systems Student Society at University
of Warsaw (O2S3@UW) consisting of:

    Igor Kotrasinski <ikotrasinsk@gmail.com>
    Karol Kosik <karo9@interia.eu>
    Ewelina Kosmider <3w3lfin@gmail.com>
    Dawid Lazarczyk <lazarczyk.dawid@gmail.com>
    Piotr Szulc <ps347277@students.mimuw.edu.pl>

Tutor and project owner:
    Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Igor Kotrasinski <i.kotrasinsk@samsung.com>
Signed-off-by: Karol Kosik <karo9@interia.eu>
[Various bug fixes and commit message update]
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/usbip/vudc_main.c

+/*
+ * Copyright (C) 2015 Karol Kosik <karo9@interia.eu>
+ * Copyright (C) 2015-2016 Samsung Electronics
+ *               Igor Kotrasinski <i.kotrasinsk@samsung.com>
+ *               Krzysztof Opasiak <k.opasiak@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/module.h>
+
+#include "vudc.h"
+
+static unsigned int vudc_number = 1;
+
+module_param_named(num, vudc_number, uint, S_IRUGO);
+MODULE_PARM_DESC(num, "number of emulated controllers");
+
+static struct platform_driver vudc_driver = {
+	.probe		= vudc_probe,
+	.remove		= vudc_remove,
+	.driver		= {
+		.name	= GADGET_NAME,
+	},
+};
+
+static struct list_head vudc_devices = LIST_HEAD_INIT(vudc_devices);
+
+static int __init init(void)
+{
+	int retval = -ENOMEM;
+	int i;
+	struct vudc_device *udc_dev = NULL, *udc_dev2 = NULL;
+
+	if (usb_disabled())
+		return -ENODEV;
+
+	if (vudc_number < 1) {
+		pr_err("Number of emulated UDC must be no less than 1");
+		return -EINVAL;
+	}
+
+	retval = platform_driver_register(&vudc_driver);
+	if (retval < 0)
+		goto out;
+
+	for (i = 0; i < vudc_number; i++) {
+		udc_dev = alloc_vudc_device(i);
+		if (!udc_dev) {
+			retval = -ENOMEM;
+			goto cleanup;
+		}
+
+		retval = platform_device_add(udc_dev->pdev);
+		if (retval < 0) {
+			put_vudc_device(udc_dev);
+			goto cleanup;
+		}
+
+		list_add_tail(&udc_dev->dev_entry, &vudc_devices);
+		if (!platform_get_drvdata(udc_dev->pdev)) {
+			/*
+			 * The udc was added successfully but its probe
+			 * function failed for some reason.
+			 */
+			retval = -EINVAL;
+			goto cleanup;
+		}
+	}
+	goto out;
+
+cleanup:
+	list_for_each_entry_safe(udc_dev, udc_dev2, &vudc_devices, dev_entry) {
+		list_del(&udc_dev->dev_entry);
+		platform_device_del(udc_dev->pdev);
+		put_vudc_device(udc_dev);
+	}
+
+	platform_driver_unregister(&vudc_driver);
+out:
+	return retval;
+}
+module_init(init);
+
+static void __exit cleanup(void)
+{
+	struct vudc_device *udc_dev = NULL, *udc_dev2 = NULL;
+
+	list_for_each_entry_safe(udc_dev, udc_dev2, &vudc_devices, dev_entry) {
+		list_del(&udc_dev->dev_entry);
+		platform_device_unregister(udc_dev->pdev);
+		put_vudc_device(udc_dev);
+	}
+	platform_driver_unregister(&vudc_driver);
+}
+module_exit(cleanup);
+
+MODULE_DESCRIPTION("USB over IP Device Controller");
+MODULE_AUTHOR("Krzysztof Opasiak, Karol Kosik, Igor Kotrasinski");
+MODULE_LICENSE("GPL");