xen: Add xenbus device driver

Access to xenbus is currently handled via xenfs. This adds a device
driver for xenbus and makes xenfs use this code.

Signed-off-by: Bastian Blank <waldi@debian.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xenbus/Makefile

@@ -1,4 +1,5 @@
 obj-y	+= xenbus.o
+obj-y	+= xenbus_dev_frontend.o
 
 xenbus-objs =
 xenbus-objs += xenbus_client.o

drivers/xen/xenbus/xenbus_comms.h

@@ -31,6 +31,8 @@
 #ifndef _XENBUS_COMMS_H
 #define _XENBUS_COMMS_H
 
+#include <linux/fs.h>
+
 int xs_init(void);
 int xb_init_comms(void);
 
@@ -43,4 +45,6 @@ int xs_input_avail(void);
 extern struct xenstore_domain_interface *xen_store_interface;
 extern int xen_store_evtchn;
 
+extern const struct file_operations xen_xenbus_fops;
+
 #endif /* _XENBUS_COMMS_H */

drivers/xen/xenbus/xenbus_dev_frontend.c

@@ -52,13 +52,16 @@
 #include <linux/namei.h>
 #include <linux/string.h>
 #include <linux/slab.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
 
-#include "xenfs.h"
-#include "../xenbus/xenbus_comms.h"
+#include "xenbus_comms.h"
 
 #include <xen/xenbus.h>
 #include <asm/xen/hypervisor.h>
 
+MODULE_LICENSE("GPL");
+
 /*
  * An element of a list of outstanding transactions, for which we're
  * still waiting a reply.
@@ -583,7 +586,7 @@ static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
 	return 0;
 }
 
-const struct file_operations xenbus_file_ops = {
+const struct file_operations xen_xenbus_fops = {
 	.read = xenbus_file_read,
 	.write = xenbus_file_write,
 	.open = xenbus_file_open,
@@ -591,3 +594,31 @@ const struct file_operations xenbus_file_ops = {
 	.poll = xenbus_file_poll,
 	.llseek = no_llseek,
 };
+EXPORT_SYMBOL_GPL(xen_xenbus_fops);
+
+static struct miscdevice xenbus_dev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "xen/xenbus",
+	.fops = &xen_xenbus_fops,
+};
+
+static int __init xenbus_init(void)
+{
+	int err;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	err = misc_register(&xenbus_dev);
+	if (err)
+		printk(KERN_ERR "Could not register xenbus device\n");
+	return err;
+}
+
+static void __exit xenbus_exit(void)
+{
+	misc_deregister(&xenbus_dev);
+}
+
+module_init(xenbus_init);
+module_exit(xenbus_exit);

drivers/xen/xenfs/Makefile

@@ -1,4 +1,4 @@
 obj-$(CONFIG_XENFS) += xenfs.o
 
-xenfs-y			  = super.o xenbus.o
+xenfs-y			  = super.o
 xenfs-$(CONFIG_XEN_DOM0) += xenstored.o

drivers/xen/xenfs/super.c

@@ -17,6 +17,7 @@
 
 #include "xenfs.h"
 #include "../privcmd.h"
+#include "../xenbus/xenbus_comms.h"
 
 #include <asm/xen/hypervisor.h>
 
@@ -83,7 +84,7 @@ static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
 {
 	static struct tree_descr xenfs_files[] = {
 		[1] = {},
-		{ "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
+		{ "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
 		{ "capabilities", &capabilities_file_ops, S_IRUGO },
 		{ "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
 		{""},

drivers/xen/xenfs/xenfs.h

@@ -1,7 +1,6 @@
 #ifndef _XENFS_XENBUS_H
 #define _XENFS_XENBUS_H
 
-extern const struct file_operations xenbus_file_ops;
 extern const struct file_operations xsd_kva_file_ops;
 extern const struct file_operations xsd_port_file_ops;