virt: Add vboxguest VMMDEV communication code

This commits adds a header describing the hardware interface for the
Virtual Box Guest PCI device used in Virtual Box virtual machines and
utility functions for talking to the Virtual Box hypervisor over this
interface.

These utility functions will used both by the vboxguest driver for the
PCI device which offers the /dev/vboxguest ioctl API and by the vboxfs
driver which offers folder sharing support.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -14562,7 +14562,9 @@ M:	Hans de Goede <hdegoede@redhat.com>
 M:	Arnd Bergmann <arnd@arndb.de>
 M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 S:	Maintained
+F:	include/linux/vbox_utils.h
 F:	include/uapi/linux/vbox*.h
+F:	drivers/virt/vboxguest/
 
 VIRTUAL SERIO DEVICE DRIVER
 M:	Stephen Chandler Paul <thatslyude@gmail.com>

include/linux/vbox_utils.h

+/* SPDX-License-Identifier: (GPL-2.0 OR CDDL-1.0) */
+/* Copyright (C) 2006-2016 Oracle Corporation */
+
+#ifndef __VBOX_UTILS_H__
+#define __VBOX_UTILS_H__
+
+#include <linux/printk.h>
+#include <linux/vbox_vmmdev_types.h>
+
+struct vbg_dev;
+
+/**
+ * vboxguest logging functions, these log both to the backdoor and call
+ * the equivalent kernel pr_foo function.
+ */
+__printf(1, 2) void vbg_info(const char *fmt, ...);
+__printf(1, 2) void vbg_warn(const char *fmt, ...);
+__printf(1, 2) void vbg_err(const char *fmt, ...);
+
+/* Only use backdoor logging for non-dynamic debug builds */
+#if defined(DEBUG) && !defined(CONFIG_DYNAMIC_DEBUG)
+__printf(1, 2) void vbg_debug(const char *fmt, ...);
+#else
+#define vbg_debug pr_debug
+#endif
+
+/**
+ * Allocate memory for generic request and initialize the request header.
+ *
+ * Return: the allocated memory
+ * @len:		Size of memory block required for the request.
+ * @req_type:		The generic request type.
+ */
+void *vbg_req_alloc(size_t len, enum vmmdev_request_type req_type);
+
+/**
+ * Perform a generic request.
+ *
+ * Return: VBox status code
+ * @gdev:		The Guest extension device.
+ * @req:		Pointer to the request structure.
+ */
+int vbg_req_perform(struct vbg_dev *gdev, void *req);
+
+int vbg_hgcm_connect(struct vbg_dev *gdev,
+		     struct vmmdev_hgcm_service_location *loc,
+		     u32 *client_id, int *vbox_status);
+
+int vbg_hgcm_disconnect(struct vbg_dev *gdev, u32 client_id, int *vbox_status);
+
+int vbg_hgcm_call(struct vbg_dev *gdev, u32 client_id, u32 function,
+		  u32 timeout_ms, struct vmmdev_hgcm_function_parameter *parms,
+		  u32 parm_count, int *vbox_status);
+
+int vbg_hgcm_call32(
+	struct vbg_dev *gdev, u32 client_id, u32 function, u32 timeout_ms,
+	struct vmmdev_hgcm_function_parameter32 *parm32, u32 parm_count,
+	int *vbox_status);
+
+/**
+ * Convert a VirtualBox status code to a standard Linux kernel return value.
+ * Return: 0 or negative errno value.
+ * @rc:			VirtualBox status code to convert.
+ */
+int vbg_status_code_to_errno(int rc);
+
+/**
+ * Helper for the vboxsf driver to get a reference to the guest device.
+ * Return: a pointer to the gdev; or a ERR_PTR value on error.
+ */
+struct vbg_dev *vbg_get_gdev(void);
+
+/**
+ * Helper for the vboxsf driver to put a guest device reference.
+ * @gdev:		Reference returned by vbg_get_gdev to put.
+ */
+void vbg_put_gdev(struct vbg_dev *gdev);
+
+#endif