/*
 *  bus driver for ccwgroup
 *
 *  Copyright IBM Corp. 2002, 2009
 *
 *  Author(s): Arnd Bergmann (arndb@de.ibm.com)
 *             Cornelia Huck (cornelia.huck@de.ibm.com)
 */
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/ctype.h>
#include <linux/dcache.h>

#include <asm/ccwdev.h>
#include <asm/ccwgroup.h>

#define CCW_BUS_ID_SIZE         20

/* In Linux 2.4, we had a channel device layer called "chandev"
 * that did all sorts of obscure stuff for networking devices.
 * This is another driver that serves as a replacement for just
 * one of its functions, namely the translation of single subchannels
 * to devices that use multiple subchannels.
 */

/* a device matches a driver if all its slave devices match the same
 * entry of the driver */
static int
ccwgroup_bus_match (struct device * dev, struct device_driver * drv)
{
        struct ccwgroup_device *gdev;
        struct ccwgroup_driver *gdrv;

        gdev = to_ccwgroupdev(dev);
        gdrv = to_ccwgroupdrv(drv);

        if (gdev->creator_id == gdrv->driver_id)
                return 1;

        return 0;
}
static int
ccwgroup_uevent (struct device *dev, struct kobj_uevent_env *env)
{
        /* TODO */
        return 0;
}

static struct bus_type ccwgroup_bus_type;

static void
__ccwgroup_remove_symlinks(struct ccwgroup_device *gdev)
{
        int i;
        char str[8];

        for (i = 0; i < gdev->count; i++) {
                sprintf(str, "cdev%d", i);
                sysfs_remove_link(&gdev->dev.kobj, str);
                sysfs_remove_link(&gdev->cdev[i]->dev.kobj, "group_device");
        }
        
}

/*
 * Provide an 'ungroup' attribute so the user can remove group devices no
 * longer needed or accidentially created. Saves memory :)
 */
static void ccwgroup_ungroup_callback(struct device *dev)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);

        mutex_lock(&gdev->reg_mutex);
        if (device_is_registered(&gdev->dev)) {
                __ccwgroup_remove_symlinks(gdev);
                device_unregister(dev);
        }
        mutex_unlock(&gdev->reg_mutex);
}

static ssize_t
ccwgroup_ungroup_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
        struct ccwgroup_device *gdev;
        int rc;

        gdev = to_ccwgroupdev(dev);

        /* Prevent concurrent online/offline processing and ungrouping. */
        if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
                return -EAGAIN;
        if (gdev->state != CCWGROUP_OFFLINE) {
                rc = -EINVAL;
                goto out;
        }
        /* Note that we cannot unregister the device from one of its
         * attribute methods, so we have to use this roundabout approach.
         */
        rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
out:
        if (rc) {
                if (rc != -EAGAIN)
                        /* Release onoff "lock" when ungrouping failed. */
                        atomic_set(&gdev->onoff, 0);
                return rc;
        }
        return count;
}

static DEVICE_ATTR(ungroup, 0200, NULL, ccwgroup_ungroup_store);

static void
ccwgroup_release (struct device *dev)
{
        struct ccwgroup_device *gdev;
        int i;

        gdev = to_ccwgroupdev(dev);

        for (i = 0; i < gdev->count; i++) {
                if (gdev->cdev[i]) {
                        if (dev_get_drvdata(&gdev->cdev[i]->dev) == gdev)
                                dev_set_drvdata(&gdev->cdev[i]->dev, NULL);
                        put_device(&gdev->cdev[i]->dev);
                }
        }
        kfree(gdev);
}

static int
__ccwgroup_create_symlinks(struct ccwgroup_device *gdev)
{
        char str[8];
        int i, rc;

        for (i = 0; i < gdev->count; i++) {
                rc = sysfs_create_link(&gdev->cdev[i]->dev.kobj, &gdev->dev.kobj,
                                       "group_device");
                if (rc) {
                        for (--i; i >= 0; i--)
                                sysfs_remove_link(&gdev->cdev[i]->dev.kobj,
                                                  "group_device");
                        return rc;
                }
        }
        for (i = 0; i < gdev->count; i++) {
                sprintf(str, "cdev%d", i);
                rc = sysfs_create_link(&gdev->dev.kobj, &gdev->cdev[i]->dev.kobj,
                                       str);
                if (rc) {
                        for (--i; i >= 0; i--) {
                                sprintf(str, "cdev%d", i);
                                sysfs_remove_link(&gdev->dev.kobj, str);
                        }
                        for (i = 0; i < gdev->count; i++)
                                sysfs_remove_link(&gdev->cdev[i]->dev.kobj,
                                                  "group_device");
                        return rc;
                }
        }
        return 0;
}

static int __get_next_bus_id(const char **buf, char *bus_id)
{
        int rc, len;
        char *start, *end;

        start = (char *)*buf;
        end = strchr(start, ',');
        if (!end) {
                /* Last entry. Strip trailing newline, if applicable. */
                end = strchr(start, '\n');
                if (end)
                        *end = '\0';
                len = strlen(start) + 1;
        } else {
                len = end - start + 1;
                end++;
        }
        if (len < CCW_BUS_ID_SIZE) {
                strlcpy(bus_id, start, len);
                rc = 0;
        } else
                rc = -EINVAL;
        *buf = end;
        return rc;
}

static int __is_valid_bus_id(char bus_id[CCW_BUS_ID_SIZE])
{
        int cssid, ssid, devno;

        /* Must be of form %x.%x.%04x */
        if (sscanf(bus_id, "%x.%1x.%04x", &cssid, &ssid, &devno) != 3)
                return 0;
        return 1;
}

/**
 * ccwgroup_create_from_string() - create and register a ccw group device
 * @root: parent device for the new device
 * @creator_id: identifier of creating driver
 * @cdrv: ccw driver of slave devices
 * @num_devices: number of slave devices
 * @buf: buffer containing comma separated bus ids of slave devices
 *
 * Create and register a new ccw group device as a child of @root. Slave
 * devices are obtained from the list of bus ids given in @buf and must all
 * belong to @cdrv.
 * Returns:
 *  %0 on success and an error code on failure.
 * Context:
 *  non-atomic
 */
int ccwgroup_create_from_string(struct device *root, unsigned int creator_id,
                                struct ccw_driver *cdrv, int num_devices,
                                const char *buf)
{
        struct ccwgroup_device *gdev;
        int rc, i;
        char tmp_bus_id[CCW_BUS_ID_SIZE];
        const char *curr_buf;

        gdev = kzalloc(sizeof(*gdev) + num_devices * sizeof(gdev->cdev[0]),
                       GFP_KERNEL);
        if (!gdev)
                return -ENOMEM;

        atomic_set(&gdev->onoff, 0);
        mutex_init(&gdev->reg_mutex);
        mutex_lock(&gdev->reg_mutex);
        gdev->creator_id = creator_id;
        gdev->count = num_devices;
        gdev->dev.bus = &ccwgroup_bus_type;
        gdev->dev.parent = root;
        gdev->dev.release = ccwgroup_release;
        device_initialize(&gdev->dev);

        curr_buf = buf;
        for (i = 0; i < num_devices && curr_buf; i++) {
                rc = __get_next_bus_id(&curr_buf, tmp_bus_id);
                if (rc != 0)
                        goto error;
                if (!__is_valid_bus_id(tmp_bus_id)) {
                        rc = -EINVAL;
                        goto error;
                }
                gdev->cdev[i] = get_ccwdev_by_busid(cdrv, tmp_bus_id);
                /*
                 * All devices have to be of the same type in
                 * order to be grouped.
                 */
                if (!gdev->cdev[i]
                    || gdev->cdev[i]->id.driver_info !=
                    gdev->cdev[0]->id.driver_info) {
                        rc = -EINVAL;
                        goto error;
                }
                /* Don't allow a device to belong to more than one group. */
                if (dev_get_drvdata(&gdev->cdev[i]->dev)) {
                        rc = -EINVAL;
                        goto error;
                }
                dev_set_drvdata(&gdev->cdev[i]->dev, gdev);
        }
        /* Check for sufficient number of bus ids. */
        if (i < num_devices && !curr_buf) {
                rc = -EINVAL;
                goto error;
        }
        /* Check for trailing stuff. */
        if (i == num_devices && strlen(curr_buf) > 0) {
                rc = -EINVAL;
                goto error;
        }

        dev_set_name(&gdev->dev, "%s", dev_name(&gdev->cdev[0]->dev));

        rc = device_add(&gdev->dev);
        if (rc)
                goto error;
        get_device(&gdev->dev);
        rc = device_create_file(&gdev->dev, &dev_attr_ungroup);

        if (rc) {
                device_unregister(&gdev->dev);
                goto error;
        }

        rc = __ccwgroup_create_symlinks(gdev);
        if (!rc) {
                mutex_unlock(&gdev->reg_mutex);
                put_device(&gdev->dev);
                return 0;
        }
        device_remove_file(&gdev->dev, &dev_attr_ungroup);
        device_unregister(&gdev->dev);
error:
        for (i = 0; i < num_devices; i++)
                if (gdev->cdev[i]) {
                        if (dev_get_drvdata(&gdev->cdev[i]->dev) == gdev)
                                dev_set_drvdata(&gdev->cdev[i]->dev, NULL);
                        put_device(&gdev->cdev[i]->dev);
                        gdev->cdev[i] = NULL;
                }
        mutex_unlock(&gdev->reg_mutex);
        put_device(&gdev->dev);
        return rc;
}
EXPORT_SYMBOL(ccwgroup_create_from_string);

static int ccwgroup_notifier(struct notifier_block *nb, unsigned long action,
                             void *data);

static struct notifier_block ccwgroup_nb = {
        .notifier_call = ccwgroup_notifier
};

static int __init init_ccwgroup(void)
{
        int ret;

        ret = bus_register(&ccwgroup_bus_type);
        if (ret)
                return ret;

        ret = bus_register_notifier(&ccwgroup_bus_type, &ccwgroup_nb);
        if (ret)
                bus_unregister(&ccwgroup_bus_type);

        return ret;
}

static void __exit cleanup_ccwgroup(void)
{
        bus_unregister_notifier(&ccwgroup_bus_type, &ccwgroup_nb);
        bus_unregister(&ccwgroup_bus_type);
}

module_init(init_ccwgroup);
module_exit(cleanup_ccwgroup);

/************************** driver stuff ******************************/

static int
ccwgroup_set_online(struct ccwgroup_device *gdev)
{
        struct ccwgroup_driver *gdrv;
        int ret;

        if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
                return -EAGAIN;
        if (gdev->state == CCWGROUP_ONLINE) {
                ret = 0;
                goto out;
        }
        if (!gdev->dev.driver) {
                ret = -EINVAL;
                goto out;
        }
        gdrv = to_ccwgroupdrv (gdev->dev.driver);
        if ((ret = gdrv->set_online ? gdrv->set_online(gdev) : 0))
                goto out;

        gdev->state = CCWGROUP_ONLINE;
 out:
        atomic_set(&gdev->onoff, 0);
        return ret;
}

static int
ccwgroup_set_offline(struct ccwgroup_device *gdev)
{
        struct ccwgroup_driver *gdrv;
        int ret;

        if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
                return -EAGAIN;
        if (gdev->state == CCWGROUP_OFFLINE) {
                ret = 0;
                goto out;
        }
        if (!gdev->dev.driver) {
                ret = -EINVAL;
                goto out;
        }
        gdrv = to_ccwgroupdrv (gdev->dev.driver);
        if ((ret = gdrv->set_offline ? gdrv->set_offline(gdev) : 0))
                goto out;

        gdev->state = CCWGROUP_OFFLINE;
 out:
        atomic_set(&gdev->onoff, 0);
        return ret;
}

static ssize_t
ccwgroup_online_store (struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
        struct ccwgroup_device *gdev;
        struct ccwgroup_driver *gdrv;
        unsigned long value;
        int ret;

        if (!dev->driver)
                return -ENODEV;

        gdev = to_ccwgroupdev(dev);
        gdrv = to_ccwgroupdrv(dev->driver);

        if (!try_module_get(gdrv->owner))
                return -EINVAL;

        ret = strict_strtoul(buf, 0, &value);
        if (ret)
                goto out;

        if (value == 1)
                ret = ccwgroup_set_online(gdev);
        else if (value == 0)
                ret = ccwgroup_set_offline(gdev);
        else
                ret = -EINVAL;
out:
        module_put(gdrv->owner);
        return (ret == 0) ? count : ret;
}

static ssize_t
ccwgroup_online_show (struct device *dev, struct device_attribute *attr, char *buf)
{
        int online;

        online = (to_ccwgroupdev(dev)->state == CCWGROUP_ONLINE);

        return sprintf(buf, online ? "1\n" : "0\n");
}

static DEVICE_ATTR(online, 0644, ccwgroup_online_show, ccwgroup_online_store);

static int
ccwgroup_probe (struct device *dev)
{
        struct ccwgroup_device *gdev;
        struct ccwgroup_driver *gdrv;

        int ret;

        gdev = to_ccwgroupdev(dev);
        gdrv = to_ccwgroupdrv(dev->driver);

        if ((ret = device_create_file(dev, &dev_attr_online)))
                return ret;

        ret = gdrv->probe ? gdrv->probe(gdev) : -ENODEV;
        if (ret)
                device_remove_file(dev, &dev_attr_online);

        return ret;
}

static int
ccwgroup_remove (struct device *dev)
{
        struct ccwgroup_device *gdev;
        struct ccwgroup_driver *gdrv;

        device_remove_file(dev, &dev_attr_online);
        device_remove_file(dev, &dev_attr_ungroup);

        if (!dev->driver)
                return 0;

        gdev = to_ccwgroupdev(dev);
        gdrv = to_ccwgroupdrv(dev->driver);

        if (gdrv->remove)
                gdrv->remove(gdev);

        return 0;
}

static void ccwgroup_shutdown(struct device *dev)
{
        struct ccwgroup_device *gdev;
        struct ccwgroup_driver *gdrv;

        if (!dev->driver)
                return;

        gdev = to_ccwgroupdev(dev);
        gdrv = to_ccwgroupdrv(dev->driver);

        if (gdrv->shutdown)
                gdrv->shutdown(gdev);
}

static int ccwgroup_pm_prepare(struct device *dev)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);

        /* Fail while device is being set online/offline. */
        if (atomic_read(&gdev->onoff))
                return -EAGAIN;

        if (!gdev->dev.driver || gdev->state != CCWGROUP_ONLINE)
                return 0;

        return gdrv->prepare ? gdrv->prepare(gdev) : 0;
}

static void ccwgroup_pm_complete(struct device *dev)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(dev->driver);

        if (!gdev->dev.driver || gdev->state != CCWGROUP_ONLINE)
                return;

        if (gdrv->complete)
                gdrv->complete(gdev);
}

static int ccwgroup_pm_freeze(struct device *dev)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);

        if (!gdev->dev.driver || gdev->state != CCWGROUP_ONLINE)
                return 0;

        return gdrv->freeze ? gdrv->freeze(gdev) : 0;
}

static int ccwgroup_pm_thaw(struct device *dev)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);

        if (!gdev->dev.driver || gdev->state != CCWGROUP_ONLINE)
                return 0;

        return gdrv->thaw ? gdrv->thaw(gdev) : 0;
}

static int ccwgroup_pm_restore(struct device *dev)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);

        if (!gdev->dev.driver || gdev->state != CCWGROUP_ONLINE)
                return 0;

        return gdrv->restore ? gdrv->restore(gdev) : 0;
}

static struct dev_pm_ops ccwgroup_pm_ops = {
        .prepare = ccwgroup_pm_prepare,
        .complete = ccwgroup_pm_complete,
        .freeze = ccwgroup_pm_freeze,
        .thaw = ccwgroup_pm_thaw,
        .restore = ccwgroup_pm_restore,
};

static struct bus_type ccwgroup_bus_type = {
        .name   = "ccwgroup",
        .match  = ccwgroup_bus_match,
        .uevent = ccwgroup_uevent,
        .probe  = ccwgroup_probe,
        .remove = ccwgroup_remove,
        .shutdown = ccwgroup_shutdown,
        .pm = &ccwgroup_pm_ops,
};


static int ccwgroup_notifier(struct notifier_block *nb, unsigned long action,
                             void *data)
{
        struct device *dev = data;

        if (action == BUS_NOTIFY_UNBIND_DRIVER)
                device_schedule_callback(dev, ccwgroup_ungroup_callback);

        return NOTIFY_OK;
}


/**
 * ccwgroup_driver_register() - register a ccw group driver
 * @cdriver: driver to be registered
 *
 * This function is mainly a wrapper around driver_register().
 */
int ccwgroup_driver_register(struct ccwgroup_driver *cdriver)
{
        /* register our new driver with the core */
        cdriver->driver.bus = &ccwgroup_bus_type;
        cdriver->driver.name = cdriver->name;
        cdriver->driver.owner = cdriver->owner;

        return driver_register(&cdriver->driver);
}

static int
__ccwgroup_match_all(struct device *dev, void *data)
{
        return 1;
}

/**
 * ccwgroup_driver_unregister() - deregister a ccw group driver
 * @cdriver: driver to be deregistered
 *
 * This function is mainly a wrapper around driver_unregister().
 */
void ccwgroup_driver_unregister(struct ccwgroup_driver *cdriver)
{
        struct device *dev;

        /* We don't want ccwgroup devices to live longer than their driver. */
        get_driver(&cdriver->driver);
        while ((dev = driver_find_device(&cdriver->driver, NULL, NULL,
                                         __ccwgroup_match_all))) {
                struct ccwgroup_device *gdev = to_ccwgroupdev(dev);

                mutex_lock(&gdev->reg_mutex);
                __ccwgroup_remove_symlinks(gdev);
                device_unregister(dev);
                mutex_unlock(&gdev->reg_mutex);
                put_device(dev);
        }
        put_driver(&cdriver->driver);
        driver_unregister(&cdriver->driver);
}

/**
 * ccwgroup_probe_ccwdev() - probe function for slave devices
 * @cdev: ccw device to be probed
 *
 * This is a dummy probe function for ccw devices that are slave devices in
 * a ccw group device.
 * Returns:
 *  always %0
 */
int ccwgroup_probe_ccwdev(struct ccw_device *cdev)
{
        return 0;
}

static struct ccwgroup_device *
__ccwgroup_get_gdev_by_cdev(struct ccw_device *cdev)
{
        struct ccwgroup_device *gdev;

        gdev = dev_get_drvdata(&cdev->dev);
        if (gdev) {
                if (get_device(&gdev->dev)) {
                        mutex_lock(&gdev->reg_mutex);
                        if (device_is_registered(&gdev->dev))
                                return gdev;
                        mutex_unlock(&gdev->reg_mutex);
                        put_device(&gdev->dev);
                }
                return NULL;
        }
        return NULL;
}

/**
 * ccwgroup_remove_ccwdev() - remove function for slave devices
 * @cdev: ccw device to be removed
 *
 * This is a remove function for ccw devices that are slave devices in a ccw
 * group device. It sets the ccw device offline and also deregisters the
 * embedding ccw group device.
 */
void ccwgroup_remove_ccwdev(struct ccw_device *cdev)
{
        struct ccwgroup_device *gdev;

        /* Ignore offlining errors, device is gone anyway. */
        ccw_device_set_offline(cdev);
        /* If one of its devices is gone, the whole group is done for. */
        gdev = __ccwgroup_get_gdev_by_cdev(cdev);
        if (gdev) {
                __ccwgroup_remove_symlinks(gdev);
                device_unregister(&gdev->dev);
                mutex_unlock(&gdev->reg_mutex);
                put_device(&gdev->dev);
        }
}

MODULE_LICENSE("GPL");
EXPORT_SYMBOL(ccwgroup_driver_register);
EXPORT_SYMBOL(ccwgroup_driver_unregister);
EXPORT_SYMBOL(ccwgroup_probe_ccwdev);
EXPORT_SYMBOL(ccwgroup_remove_ccwdev);