xenbus_probe_backend.c

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/******************************************************************************
 * Talks to Xen Store to figure out what devices we have (backend half).
 *
 * Copyright (C) 2005 Rusty Russell, IBM Corporation
 * Copyright (C) 2005 Mike Wray, Hewlett-Packard
 * Copyright (C) 2005, 2006 XenSource Ltd
 * Copyright (C) 2007 Solarflare Communications, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define DPRINTK(fmt, args...)               \
    pr_debug("xenbus_probe (%s:%d) " fmt ".\n", \
         __func__, __LINE__, ##args)

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/notifier.h>
#include <linux/export.h>

#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/xen/hypervisor.h>
#include <asm/hypervisor.h>
#include <xen/xenbus.h>
#include <xen/features.h>

#include "xenbus_comms.h"
#include "xenbus_probe.h"

/* backend/<type>/<fe-uuid>/<id> => <type>-<fe-domid>-<id> */
static int backend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char *nodename)
{
    int domid, err;
    const char *devid, *type, *frontend;
    unsigned int typelen;

    type = strchr(nodename, '/');
    if (!type)
        return -EINVAL;
    type++;
    typelen = strcspn(type, "/");
    if (!typelen || type[typelen] != '/')
        return -EINVAL;

    devid = strrchr(nodename, '/') + 1;

    err = xenbus_gather(XBT_NIL, nodename, "frontend-id", "%i", &domid,
                "frontend", NULL, &frontend,
                NULL);
    if (err)
        return err;
    if (strlen(frontend) == 0)
        err = -ERANGE;
    if (!err && !xenbus_exists(XBT_NIL, frontend, ""))
        err = -ENOENT;
    kfree(frontend);

    if (err)
        return err;

    if (snprintf(bus_id, XEN_BUS_ID_SIZE, "%.*s-%i-%s",
             typelen, type, domid, devid) >= XEN_BUS_ID_SIZE)
        return -ENOSPC;
    return 0;
}

static int xenbus_uevent_backend(struct device *dev,
                 struct kobj_uevent_env *env)
{
    struct xenbus_device *xdev;
    struct xenbus_driver *drv;
    struct xen_bus_type *bus;

    DPRINTK("");

    if (dev == NULL)
        return -ENODEV;

    xdev = to_xenbus_device(dev);
    bus = container_of(xdev->dev.bus, struct xen_bus_type, bus);

    if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
        return -ENOMEM;

    /* stuff we want to pass to /sbin/hotplug */
    if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
        return -ENOMEM;

    if (add_uevent_var(env, "XENBUS_PATH=%s", xdev->nodename))
        return -ENOMEM;

    if (add_uevent_var(env, "XENBUS_BASE_PATH=%s", bus->root))
        return -ENOMEM;

    if (dev->driver) {
        drv = to_xenbus_driver(dev->driver);
        if (drv && drv->uevent)
            return drv->uevent(xdev, env);
    }

    return 0;
}

/* backend/<typename>/<frontend-uuid>/<name> */
static int xenbus_probe_backend_unit(struct xen_bus_type *bus,
                     const char *dir,
                     const char *type,
                     const char *name)
{
    char *nodename;
    int err;

    nodename = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
    if (!nodename)
        return -ENOMEM;

    DPRINTK("%s\n", nodename);

    err = xenbus_probe_node(bus, type, nodename);
    kfree(nodename);
    return err;
}

/* backend/<typename>/<frontend-domid> */
static int xenbus_probe_backend(struct xen_bus_type *bus, const char *type,
                const char *domid)
{
    char *nodename;
    int err = 0;
    char **dir;
    unsigned int i, dir_n = 0;

    DPRINTK("");

    nodename = kasprintf(GFP_KERNEL, "%s/%s/%s", bus->root, type, domid);
    if (!nodename)
        return -ENOMEM;

    dir = xenbus_directory(XBT_NIL, nodename, "", &dir_n);
    if (IS_ERR(dir)) {
        kfree(nodename);
        return PTR_ERR(dir);
    }

    for (i = 0; i < dir_n; i++) {
        err = xenbus_probe_backend_unit(bus, nodename, type, dir[i]);
        if (err)
            break;
    }
    kfree(dir);
    kfree(nodename);
    return err;
}

static void frontend_changed(struct xenbus_watch *watch,
                const char **vec, unsigned int len)
{
    xenbus_otherend_changed(watch, vec, len, 0);
}

static struct xen_bus_type xenbus_backend = {
    .root = "backend",
    .levels = 3,        /* backend/type/<frontend>/<id> */
    .get_bus_id = backend_bus_id,
    .probe = xenbus_probe_backend,
    .otherend_changed = frontend_changed,
    .bus = {
        .name       = "xen-backend",
        .match      = xenbus_match,
        .uevent     = xenbus_uevent_backend,
        .probe      = xenbus_dev_probe,
        .remove     = xenbus_dev_remove,
        .shutdown   = xenbus_dev_shutdown,
        .dev_attrs  = xenbus_dev_attrs,
    },
};

static void backend_changed(struct xenbus_watch *watch,
                const char **vec, unsigned int len)
{
    DPRINTK("");

    xenbus_dev_changed(vec[XS_WATCH_PATH], &xenbus_backend);
}

static struct xenbus_watch be_watch = {
    .node = "backend",
    .callback = backend_changed,
};

static int read_frontend_details(struct xenbus_device *xendev)
{
    return xenbus_read_otherend_details(xendev, "frontend-id", "frontend");
}

int xenbus_dev_is_online(struct xenbus_device *dev)
{
    int rc, val;

    rc = xenbus_scanf(XBT_NIL, dev->nodename, "online", "%d", &val);
    if (rc != 1)
        val = 0; /* no online node present */

    return val;
}
EXPORT_SYMBOL_GPL(xenbus_dev_is_online);

int xenbus_register_backend(struct xenbus_driver *drv)
{
    drv->read_otherend_details = read_frontend_details;

    return xenbus_register_driver_common(drv, &xenbus_backend);
}
EXPORT_SYMBOL_GPL(xenbus_register_backend);

static int backend_probe_and_watch(struct notifier_block *notifier,
                   unsigned long event,
                   void *data)
{
    /* Enumerate devices in xenstore and watch for changes. */
    xenbus_probe_devices(&xenbus_backend);
    register_xenbus_watch(&be_watch);

    return NOTIFY_DONE;
}

static int __init xenbus_probe_backend_init(void)
{
    static struct notifier_block xenstore_notifier = {
        .notifier_call = backend_probe_and_watch
    };
    int err;

    DPRINTK("");

    /* Register ourselves with the kernel bus subsystem */
    err = bus_register(&xenbus_backend.bus);
    if (err)
        return err;

    register_xenstore_notifier(&xenstore_notifier);

    return 0;
}
subsys_initcall(xenbus_probe_backend_init);