virtio-9p: Create a commandline option -fsdev

This patch creates a new command line option named -fsdev to hold any file
system specific information.

The option will currently hold the following attributes:
-fsdev fstype id=id,path=path_to_share
where
fstype: Type of the file system.
id:     Identifier used to refer to this fsdev
path:   The path on the host that is identified by this fsdev.

[aneesh.kumar@linux.vnet.ibm.com: Abstraction using FsContext]
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

fsdev/qemu-fsdev.h

@@ -0,0 +1,53 @@
+/*
+ * Virtio 9p
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Gautham R Shenoy <ego@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#ifndef QEMU_FSDEV_H
+#define QEMU_FSDEV_H
+#include "qemu-option.h"
+#include "hw/file-op-9p.h"
+
+
+/*
+ * A table to store the various file systems and their callback operations.
+ * -----------------
+ * fstype | ops
+ * -----------------
+ *  local | local_ops
+ *  .     |
+ *  .     |
+ *  .     |
+ *  .     |
+ * -----------------
+ *  etc
+ */
+typedef struct FsTypeTable {
+    const char *name;
+    FileOperations *ops;
+} FsTypeTable;
+
+/*
+ * Structure to store the various fsdev's passed through command line.
+ */
+typedef struct FsTypeEntry {
+    char *fsdev_id;
+    char *path;
+    FileOperations *ops;
+} FsTypeEntry;
+
+typedef struct FsTypeListEntry {
+    FsTypeEntry fse;
+    QTAILQ_ENTRY(FsTypeListEntry) next;
+} FsTypeListEntry;
+
+extern int qemu_fsdev_add(QemuOpts *opts);
+extern FsTypeEntry *get_fsdev_fsentry(char *id);
+#endif