/*
 * System Trace Module (STM) master/channel allocation policy management
 * Copyright (c) 2014, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.
 *
 * A master/channel allocation policy allows mapping string identifiers to
 * master and channel ranges, where allocation can be done.
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/configfs.h>
#include <linux/slab.h>
#include <linux/stm.h>
#include "stm.h"

/*
 * STP Master/Channel allocation policy configfs layout.
 */

struct stp_policy {
        struct config_group     group;
        struct stm_device       *stm;
};

struct stp_policy_node {
        struct config_group     group;
        struct stp_policy       *policy;
        unsigned int            first_master;
        unsigned int            last_master;
        unsigned int            first_channel;
        unsigned int            last_channel;
};

static struct configfs_subsystem stp_policy_subsys;

void stp_policy_node_get_ranges(struct stp_policy_node *policy_node,
                                unsigned int *mstart, unsigned int *mend,
                                unsigned int *cstart, unsigned int *cend)
{
        *mstart = policy_node->first_master;
        *mend   = policy_node->last_master;
        *cstart = policy_node->first_channel;
        *cend   = policy_node->last_channel;
}

static inline char *stp_policy_node_name(struct stp_policy_node *policy_node)
{
        return policy_node->group.cg_item.ci_name ? : "<none>";
}

static inline struct stp_policy *to_stp_policy(struct config_item *item)
{
        return item ?
                container_of(to_config_group(item), struct stp_policy, group) :
                NULL;
}

static inline struct stp_policy_node *
to_stp_policy_node(struct config_item *item)
{
        return item ?
                container_of(to_config_group(item), struct stp_policy_node,
                             group) :
                NULL;
}

static ssize_t
stp_policy_node_masters_show(struct config_item *item, char *page)
{
        struct stp_policy_node *policy_node = to_stp_policy_node(item);
        ssize_t count;

        count = sprintf(page, "%u %u\n", policy_node->first_master,
                        policy_node->last_master);

        return count;
}

static ssize_t
stp_policy_node_masters_store(struct config_item *item, const char *page,
                              size_t count)
{
        struct stp_policy_node *policy_node = to_stp_policy_node(item);
        unsigned int first, last;
        struct stm_device *stm;
        char *p = (char *)page;
        ssize_t ret = -ENODEV;

        if (sscanf(p, "%u %u", &first, &last) != 2)
                return -EINVAL;

        mutex_lock(&stp_policy_subsys.su_mutex);
        stm = policy_node->policy->stm;
        if (!stm)
                goto unlock;

        /* must be within [sw_start..sw_end], which is an inclusive range */
        if (first > last || first < stm->data->sw_start ||
            last > stm->data->sw_end) {
                ret = -ERANGE;
                goto unlock;
        }

        ret = count;
        policy_node->first_master = first;
        policy_node->last_master = last;

unlock:
        mutex_unlock(&stp_policy_subsys.su_mutex);

        return ret;
}

static ssize_t
stp_policy_node_channels_show(struct config_item *item, char *page)
{
        struct stp_policy_node *policy_node = to_stp_policy_node(item);
        ssize_t count;

        count = sprintf(page, "%u %u\n", policy_node->first_channel,
                        policy_node->last_channel);

        return count;
}

static ssize_t
stp_policy_node_channels_store(struct config_item *item, const char *page,
                               size_t count)
{
        struct stp_policy_node *policy_node = to_stp_policy_node(item);
        unsigned int first, last;
        struct stm_device *stm;
        char *p = (char *)page;
        ssize_t ret = -ENODEV;

        if (sscanf(p, "%u %u", &first, &last) != 2)
                return -EINVAL;

        mutex_lock(&stp_policy_subsys.su_mutex);
        stm = policy_node->policy->stm;
        if (!stm)
                goto unlock;

        if (first > INT_MAX || last > INT_MAX || first > last ||
            last >= stm->data->sw_nchannels) {
                ret = -ERANGE;
                goto unlock;
        }

        ret = count;
        policy_node->first_channel = first;
        policy_node->last_channel = last;

unlock:
        mutex_unlock(&stp_policy_subsys.su_mutex);

        return ret;
}

static void stp_policy_node_release(struct config_item *item)
{
        kfree(to_stp_policy_node(item));
}

static struct configfs_item_operations stp_policy_node_item_ops = {
        .release                = stp_policy_node_release,
};

CONFIGFS_ATTR(stp_policy_node_, masters);
CONFIGFS_ATTR(stp_policy_node_, channels);

static struct configfs_attribute *stp_policy_node_attrs[] = {
        &stp_policy_node_attr_masters,
        &stp_policy_node_attr_channels,
        NULL,
};

static struct config_item_type stp_policy_type;
static struct config_item_type stp_policy_node_type;

static struct config_group *
stp_policy_node_make(struct config_group *group, const char *name)
{
        struct stp_policy_node *policy_node, *parent_node;
        struct stp_policy *policy;

        if (group->cg_item.ci_type == &stp_policy_type) {
                policy = container_of(group, struct stp_policy, group);
        } else {
                parent_node = container_of(group, struct stp_policy_node,
                                           group);
                policy = parent_node->policy;
        }

        if (!policy->stm)
                return ERR_PTR(-ENODEV);

        policy_node = kzalloc(sizeof(struct stp_policy_node), GFP_KERNEL);
        if (!policy_node)
                return ERR_PTR(-ENOMEM);

        config_group_init_type_name(&policy_node->group, name,
                                    &stp_policy_node_type);

        policy_node->policy = policy;

        /* default values for the attributes */
        policy_node->first_master = policy->stm->data->sw_start;
        policy_node->last_master = policy->stm->data->sw_end;
        policy_node->first_channel = 0;
        policy_node->last_channel = policy->stm->data->sw_nchannels - 1;

        return &policy_node->group;
}

static void
stp_policy_node_drop(struct config_group *group, struct config_item *item)
{
        config_item_put(item);
}

static struct configfs_group_operations stp_policy_node_group_ops = {
        .make_group     = stp_policy_node_make,
        .drop_item      = stp_policy_node_drop,
};

static struct config_item_type stp_policy_node_type = {
        .ct_item_ops    = &stp_policy_node_item_ops,
        .ct_group_ops   = &stp_policy_node_group_ops,
        .ct_attrs       = stp_policy_node_attrs,
        .ct_owner       = THIS_MODULE,
};

/*
 * Root group: policies.
 */
static ssize_t stp_policy_device_show(struct config_item *item,
                                      char *page)
{
        struct stp_policy *policy = to_stp_policy(item);
        ssize_t count;

        count = sprintf(page, "%s\n",
                        (policy && policy->stm) ?
                        policy->stm->data->name :
                        "<none>");

        return count;
}

CONFIGFS_ATTR_RO(stp_policy_, device);

static struct configfs_attribute *stp_policy_attrs[] = {
        &stp_policy_attr_device,
        NULL,
};

void stp_policy_unbind(struct stp_policy *policy)
{
        struct stm_device *stm = policy->stm;

        /*
         * stp_policy_release() will not call here if the policy is already
         * unbound; other users should not either, as no link exists between
         * this policy and anything else in that case
         */
        if (WARN_ON_ONCE(!policy->stm))
                return;

        lockdep_assert_held(&stm->policy_mutex);

        stm->policy = NULL;
        policy->stm = NULL;

        stm_put_device(stm);
}

static void stp_policy_release(struct config_item *item)
{
        struct stp_policy *policy = to_stp_policy(item);
        struct stm_device *stm = policy->stm;

        /* a policy *can* be unbound and still exist in configfs tree */
        if (!stm)
                return;

        mutex_lock(&stm->policy_mutex);
        stp_policy_unbind(policy);
        mutex_unlock(&stm->policy_mutex);

        kfree(policy);
}

static struct configfs_item_operations stp_policy_item_ops = {
        .release                = stp_policy_release,
};

static struct configfs_group_operations stp_policy_group_ops = {
        .make_group     = stp_policy_node_make,
};

static struct config_item_type stp_policy_type = {
        .ct_item_ops    = &stp_policy_item_ops,
        .ct_group_ops   = &stp_policy_group_ops,
        .ct_attrs       = stp_policy_attrs,
        .ct_owner       = THIS_MODULE,
};

static struct config_group *
stp_policies_make(struct config_group *group, const char *name)
{
        struct config_group *ret;
        struct stm_device *stm;
        char *devname, *p;

        devname = kasprintf(GFP_KERNEL, "%s", name);
        if (!devname)
                return ERR_PTR(-ENOMEM);

        /*
         * node must look like <device_name>.<policy_name>, where
         * <device_name> is the name of an existing stm device; may
         *               contain dots;
         * <policy_name> is an arbitrary string; may not contain dots
         */
        p = strrchr(devname, '.');
        if (!p) {
                kfree(devname);
                return ERR_PTR(-EINVAL);
        }

        *p = '\0';

        stm = stm_find_device(devname);
        kfree(devname);

        if (!stm)
                return ERR_PTR(-ENODEV);

        mutex_lock(&stm->policy_mutex);
        if (stm->policy) {
                ret = ERR_PTR(-EBUSY);
                goto unlock_policy;
        }

        stm->policy = kzalloc(sizeof(*stm->policy), GFP_KERNEL);
        if (!stm->policy) {
                ret = ERR_PTR(-ENOMEM);
                goto unlock_policy;
        }

        config_group_init_type_name(&stm->policy->group, name,
                                    &stp_policy_type);
        stm->policy->stm = stm;

        ret = &stm->policy->group;

unlock_policy:
        mutex_unlock(&stm->policy_mutex);

        if (IS_ERR(ret))
                stm_put_device(stm);

        return ret;
}

static struct configfs_group_operations stp_policies_group_ops = {
        .make_group     = stp_policies_make,
};

static struct config_item_type stp_policies_type = {
        .ct_group_ops   = &stp_policies_group_ops,
        .ct_owner       = THIS_MODULE,
};

static struct configfs_subsystem stp_policy_subsys = {
        .su_group = {
                .cg_item = {
                        .ci_namebuf     = "stp-policy",
                        .ci_type        = &stp_policies_type,
                },
        },
};

/*
 * Lock the policy mutex from the outside
 */
static struct stp_policy_node *
__stp_policy_node_lookup(struct stp_policy *policy, char *s)
{
        struct stp_policy_node *policy_node, *ret;
        struct list_head *head = &policy->group.cg_children;
        struct config_item *item;
        char *start, *end = s;

        if (list_empty(head))
                return NULL;

        /* return the first entry if everything else fails */
        item = list_entry(head->next, struct config_item, ci_entry);
        ret = to_stp_policy_node(item);

next:
        for (;;) {
                start = strsep(&end, "/");
                if (!start)
                        break;

                if (!*start)
                        continue;

                list_for_each_entry(item, head, ci_entry) {
                        policy_node = to_stp_policy_node(item);

                        if (!strcmp(start,
                                    policy_node->group.cg_item.ci_name)) {
                                ret = policy_node;

                                if (!end)
                                        goto out;

                                head = &policy_node->group.cg_children;
                                goto next;
                        }
                }
                break;
        }

out:
        return ret;
}


struct stp_policy_node *
stp_policy_node_lookup(struct stm_device *stm, char *s)
{
        struct stp_policy_node *policy_node = NULL;

        mutex_lock(&stp_policy_subsys.su_mutex);

        mutex_lock(&stm->policy_mutex);
        if (stm->policy)
                policy_node = __stp_policy_node_lookup(stm->policy, s);
        mutex_unlock(&stm->policy_mutex);

        if (policy_node)
                config_item_get(&policy_node->group.cg_item);
        mutex_unlock(&stp_policy_subsys.su_mutex);

        return policy_node;
}

void stp_policy_node_put(struct stp_policy_node *policy_node)
{
        config_item_put(&policy_node->group.cg_item);
}

int __init stp_configfs_init(void)
{
        int err;

        config_group_init(&stp_policy_subsys.su_group);
        mutex_init(&stp_policy_subsys.su_mutex);
        err = configfs_register_subsystem(&stp_policy_subsys);

        return err;
}

void __exit stp_configfs_exit(void)
{
        configfs_unregister_subsystem(&stp_policy_subsys);
}