/*
 * SCSI device handler infrastruture.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright IBM Corporation, 2007
 *      Authors:
 *               Chandra Seetharaman <sekharan@us.ibm.com>
 *               Mike Anderson <andmike@linux.vnet.ibm.com>
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <scsi/scsi_dh.h>
#include "scsi_priv.h"

static DEFINE_SPINLOCK(list_lock);
static LIST_HEAD(scsi_dh_list);

struct scsi_dh_blist {
        const char *vendor;
        const char *model;
        const char *driver;
};

static const struct scsi_dh_blist scsi_dh_blist[] = {
        {"DGC", "RAID",                 "clariion" },
        {"DGC", "DISK",                 "clariion" },
        {"DGC", "VRAID",                "clariion" },

        {"COMPAQ", "MSA1000 VOLUME",    "hp_sw" },
        {"COMPAQ", "HSV110",            "hp_sw" },
        {"HP", "HSV100",                "hp_sw"},
        {"DEC", "HSG80",                "hp_sw"},

        {"IBM", "1722",                 "rdac", },
        {"IBM", "1724",                 "rdac", },
        {"IBM", "1726",                 "rdac", },
        {"IBM", "1742",                 "rdac", },
        {"IBM", "1745",                 "rdac", },
        {"IBM", "1746",                 "rdac", },
        {"IBM", "1813",                 "rdac", },
        {"IBM", "1814",                 "rdac", },
        {"IBM", "1815",                 "rdac", },
        {"IBM", "1818",                 "rdac", },
        {"IBM", "3526",                 "rdac", },
        {"SGI", "TP9",                  "rdac", },
        {"SGI", "IS",                   "rdac", },
        {"STK", "OPENstorage D280",     "rdac", },
        {"STK", "FLEXLINE 380",         "rdac", },
        {"SUN", "CSM",                  "rdac", },
        {"SUN", "LCSM100",              "rdac", },
        {"SUN", "STK6580_6780",         "rdac", },
        {"SUN", "SUN_6180",             "rdac", },
        {"SUN", "ArrayStorage",         "rdac", },
        {"DELL", "MD3",                 "rdac", },
        {"NETAPP", "INF-01-00",         "rdac", },
        {"LSI", "INF-01-00",            "rdac", },
        {"ENGENIO", "INF-01-00",        "rdac", },
        {NULL, NULL,                    NULL },
};

static const char *
scsi_dh_find_driver(struct scsi_device *sdev)
{
        const struct scsi_dh_blist *b;

        if (scsi_device_tpgs(sdev))
                return "alua";

        for (b = scsi_dh_blist; b->vendor; b++) {
                if (!strncmp(sdev->vendor, b->vendor, strlen(b->vendor)) &&
                    !strncmp(sdev->model, b->model, strlen(b->model))) {
                        return b->driver;
                }
        }
        return NULL;
}


static struct scsi_device_handler *__scsi_dh_lookup(const char *name)
{
        struct scsi_device_handler *tmp, *found = NULL;

        spin_lock(&list_lock);
        list_for_each_entry(tmp, &scsi_dh_list, list) {
                if (!strncmp(tmp->name, name, strlen(tmp->name))) {
                        found = tmp;
                        break;
                }
        }
        spin_unlock(&list_lock);
        return found;
}

static struct scsi_device_handler *scsi_dh_lookup(const char *name)
{
        struct scsi_device_handler *dh;

        dh = __scsi_dh_lookup(name);
        if (!dh) {
                request_module("scsi_dh_%s", name);
                dh = __scsi_dh_lookup(name);
        }

        return dh;
}

/*
 * scsi_dh_handler_attach - Attach a device handler to a device
 * @sdev - SCSI device the device handler should attach to
 * @scsi_dh - The device handler to attach
 */
static int scsi_dh_handler_attach(struct scsi_device *sdev,
                                  struct scsi_device_handler *scsi_dh)
{
        int error;

        if (!try_module_get(scsi_dh->module))
                return -EINVAL;

        error = scsi_dh->attach(sdev);
        if (error) {
                sdev_printk(KERN_ERR, sdev, "%s: Attach failed (%d)\n",
                            scsi_dh->name, error);
                module_put(scsi_dh->module);
        } else
                sdev->handler = scsi_dh;

        return error;
}

/*
 * scsi_dh_handler_detach - Detach a device handler from a device
 * @sdev - SCSI device the device handler should be detached from
 */
static void scsi_dh_handler_detach(struct scsi_device *sdev)
{
        sdev->handler->detach(sdev);
        sdev_printk(KERN_NOTICE, sdev, "%s: Detached\n", sdev->handler->name);
        module_put(sdev->handler->module);
}

/*
 * Functions for sysfs attribute 'dh_state'
 */
static ssize_t
store_dh_state(struct device *dev, struct device_attribute *attr,
               const char *buf, size_t count)
{
        struct scsi_device *sdev = to_scsi_device(dev);
        struct scsi_device_handler *scsi_dh;
        int err = -EINVAL;

        if (sdev->sdev_state == SDEV_CANCEL ||
            sdev->sdev_state == SDEV_DEL)
                return -ENODEV;

        if (!sdev->handler) {
                /*
                 * Attach to a device handler
                 */
                scsi_dh = scsi_dh_lookup(buf);
                if (!scsi_dh)
                        return err;
                err = scsi_dh_handler_attach(sdev, scsi_dh);
        } else {
                if (!strncmp(buf, "detach", 6)) {
                        /*
                         * Detach from a device handler
                         */
                        sdev_printk(KERN_WARNING, sdev,
                                    "can't detach handler %s.\n",
                                    sdev->handler->name);
                        err = -EINVAL;
                } else if (!strncmp(buf, "activate", 8)) {
                        /*
                         * Activate a device handler
                         */
                        if (sdev->handler->activate)
                                err = sdev->handler->activate(sdev, NULL, NULL);
                        else
                                err = 0;
                }
        }

        return err<0?err:count;
}

static ssize_t
show_dh_state(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct scsi_device *sdev = to_scsi_device(dev);

        if (!sdev->handler)
                return snprintf(buf, 20, "detached\n");

        return snprintf(buf, 20, "%s\n", sdev->handler->name);
}

static struct device_attribute scsi_dh_state_attr =
        __ATTR(dh_state, S_IRUGO | S_IWUSR, show_dh_state,
               store_dh_state);

int scsi_dh_add_device(struct scsi_device *sdev)
{
        struct scsi_device_handler *devinfo = NULL;
        const char *drv;
        int err;

        err = device_create_file(&sdev->sdev_gendev, &scsi_dh_state_attr);
        if (err)
                return err;

        drv = scsi_dh_find_driver(sdev);
        if (drv)
                devinfo = __scsi_dh_lookup(drv);
        if (devinfo)
                err = scsi_dh_handler_attach(sdev, devinfo);
        return err;
}

void scsi_dh_release_device(struct scsi_device *sdev)
{
        if (sdev->handler)
                scsi_dh_handler_detach(sdev);
}

void scsi_dh_remove_device(struct scsi_device *sdev)
{
        device_remove_file(&sdev->sdev_gendev, &scsi_dh_state_attr);
}

/*
 * scsi_register_device_handler - register a device handler personality
 *      module.
 * @scsi_dh - device handler to be registered.
 *
 * Returns 0 on success, -EBUSY if handler already registered.
 */
int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)
{
        if (__scsi_dh_lookup(scsi_dh->name))
                return -EBUSY;

        if (!scsi_dh->attach || !scsi_dh->detach)
                return -EINVAL;

        spin_lock(&list_lock);
        list_add(&scsi_dh->list, &scsi_dh_list);
        spin_unlock(&list_lock);

        printk(KERN_INFO "%s: device handler registered\n", scsi_dh->name);

        return SCSI_DH_OK;
}
EXPORT_SYMBOL_GPL(scsi_register_device_handler);

/*
 * scsi_unregister_device_handler - register a device handler personality
 *      module.
 * @scsi_dh - device handler to be unregistered.
 *
 * Returns 0 on success, -ENODEV if handler not registered.
 */
int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh)
{
        if (!__scsi_dh_lookup(scsi_dh->name))
                return -ENODEV;

        spin_lock(&list_lock);
        list_del(&scsi_dh->list);
        spin_unlock(&list_lock);
        printk(KERN_INFO "%s: device handler unregistered\n", scsi_dh->name);

        return SCSI_DH_OK;
}
EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);

static struct scsi_device *get_sdev_from_queue(struct request_queue *q)
{
        struct scsi_device *sdev;
        unsigned long flags;

        spin_lock_irqsave(q->queue_lock, flags);
        sdev = q->queuedata;
        if (!sdev || !get_device(&sdev->sdev_gendev))
                sdev = NULL;
        spin_unlock_irqrestore(q->queue_lock, flags);

        return sdev;
}

/*
 * scsi_dh_activate - activate the path associated with the scsi_device
 *      corresponding to the given request queue.
 *     Returns immediately without waiting for activation to be completed.
 * @q    - Request queue that is associated with the scsi_device to be
 *         activated.
 * @fn   - Function to be called upon completion of the activation.
 *         Function fn is called with data (below) and the error code.
 *         Function fn may be called from the same calling context. So,
 *         do not hold the lock in the caller which may be needed in fn.
 * @data - data passed to the function fn upon completion.
 *
 */
int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data)
{
        struct scsi_device *sdev;
        int err = SCSI_DH_NOSYS;

        sdev = get_sdev_from_queue(q);
        if (!sdev) {
                if (fn)
                        fn(data, err);
                return err;
        }

        if (!sdev->handler)
                goto out_fn;
        err = SCSI_DH_NOTCONN;
        if (sdev->sdev_state == SDEV_CANCEL ||
            sdev->sdev_state == SDEV_DEL)
                goto out_fn;

        err = SCSI_DH_DEV_OFFLINED;
        if (sdev->sdev_state == SDEV_OFFLINE)
                goto out_fn;

        if (sdev->handler->activate)
                err = sdev->handler->activate(sdev, fn, data);

out_put_device:
        put_device(&sdev->sdev_gendev);
        return err;

out_fn:
        if (fn)
                fn(data, err);
        goto out_put_device;
}
EXPORT_SYMBOL_GPL(scsi_dh_activate);

/*
 * scsi_dh_set_params - set the parameters for the device as per the
 *      string specified in params.
 * @q - Request queue that is associated with the scsi_device for
 *      which the parameters to be set.
 * @params - parameters in the following format
 *      "no_of_params\0param1\0param2\0param3\0...\0"
 *      for example, string for 2 parameters with value 10 and 21
 *      is specified as "2\010\021\0".
 */
int scsi_dh_set_params(struct request_queue *q, const char *params)
{
        struct scsi_device *sdev;
        int err = -SCSI_DH_NOSYS;

        sdev = get_sdev_from_queue(q);
        if (!sdev)
                return err;

        if (sdev->handler && sdev->handler->set_params)
                err = sdev->handler->set_params(sdev, params);
        put_device(&sdev->sdev_gendev);
        return err;
}
EXPORT_SYMBOL_GPL(scsi_dh_set_params);

/*
 * scsi_dh_attach - Attach device handler
 * @q - Request queue that is associated with the scsi_device
 *      the handler should be attached to
 * @name - name of the handler to attach
 */
int scsi_dh_attach(struct request_queue *q, const char *name)
{
        struct scsi_device *sdev;
        struct scsi_device_handler *scsi_dh;
        int err = 0;

        sdev = get_sdev_from_queue(q);
        if (!sdev)
                return -ENODEV;

        scsi_dh = scsi_dh_lookup(name);
        if (!scsi_dh) {
                err = -EINVAL;
                goto out_put_device;
        }

        if (sdev->handler) {
                if (sdev->handler != scsi_dh)
                        err = -EBUSY;
                goto out_put_device;
        }

        err = scsi_dh_handler_attach(sdev, scsi_dh);

out_put_device:
        put_device(&sdev->sdev_gendev);
        return err;
}
EXPORT_SYMBOL_GPL(scsi_dh_attach);

/*
 * scsi_dh_attached_handler_name - Get attached device handler's name
 * @q - Request queue that is associated with the scsi_device
 *      that may have a device handler attached
 * @gfp - the GFP mask used in the kmalloc() call when allocating memory
 *
 * Returns name of attached handler, NULL if no handler is attached.
 * Caller must take care to free the returned string.
 */
const char *scsi_dh_attached_handler_name(struct request_queue *q, gfp_t gfp)
{
        struct scsi_device *sdev;
        const char *handler_name = NULL;

        sdev = get_sdev_from_queue(q);
        if (!sdev)
                return NULL;

        if (sdev->handler)
                handler_name = kstrdup(sdev->handler->name, gfp);
        put_device(&sdev->sdev_gendev);
        return handler_name;
}
EXPORT_SYMBOL_GPL(scsi_dh_attached_handler_name);