// SPDX-License-Identifier: GPL-2.0
/*
 * System Control and Management Interface (SCMI) Message Protocol bus layer
 *
 * Copyright (C) 2018-2021 ARM Ltd.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/atomic.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/device.h>

#include "common.h"

#define SCMI_UEVENT_MODALIAS_FMT        "%s:%02x:%s"

BLOCKING_NOTIFIER_HEAD(scmi_requested_devices_nh);
EXPORT_SYMBOL_GPL(scmi_requested_devices_nh);

static DEFINE_IDA(scmi_bus_id);

static DEFINE_IDR(scmi_requested_devices);
/* Protect access to scmi_requested_devices */
static DEFINE_MUTEX(scmi_requested_devices_mtx);

struct scmi_requested_dev {
        const struct scmi_device_id *id_table;
        struct list_head node;
};

/* Track globally the creation of SCMI SystemPower related devices */
static atomic_t scmi_syspower_registered = ATOMIC_INIT(0);

/**
 * scmi_protocol_device_request  - Helper to request a device
 *
 * @id_table: A protocol/name pair descriptor for the device to be created.
 *
 * This helper let an SCMI driver request specific devices identified by the
 * @id_table to be created for each active SCMI instance.
 *
 * The requested device name MUST NOT be already existent for this protocol;
 * at first the freshly requested @id_table is annotated in the IDR table
 * @scmi_requested_devices and then the requested device is advertised to any
 * registered party via the @scmi_requested_devices_nh notification chain.
 *
 * Return: 0 on Success
 */
static int scmi_protocol_device_request(const struct scmi_device_id *id_table)
{
        int ret = 0;
        struct list_head *head, *phead = NULL;
        struct scmi_requested_dev *rdev;

        pr_debug("Requesting SCMI device (%s) for protocol %x\n",
                 id_table->name, id_table->protocol_id);

        if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT) &&
            !IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX)) {
                pr_warn("SCMI Raw mode active. Rejecting '%s'/0x%02X\n",
                        id_table->name, id_table->protocol_id);
                return -EINVAL;
        }

        /*
         * Find the matching protocol rdev list and then search of any
         * existent equally named device...fails if any duplicate found.
         */
        mutex_lock(&scmi_requested_devices_mtx);
        phead = idr_find(&scmi_requested_devices, id_table->protocol_id);
        if (phead) {
                head = phead;
                list_for_each_entry(rdev, head, node) {
                        if (!strcmp(rdev->id_table->name, id_table->name)) {
                                pr_err("Ignoring duplicate request [%d] %s\n",
                                       rdev->id_table->protocol_id,
                                       rdev->id_table->name);
                                ret = -EINVAL;
                                goto out;
                        }
                }
        }

        /*
         * No duplicate found for requested id_table, so let's create a new
         * requested device entry for this new valid request.
         */
        rdev = kzalloc_obj(*rdev);
        if (!rdev) {
                ret = -ENOMEM;
                goto out;
        }
        rdev->id_table = id_table;

        /*
         * Append the new requested device table descriptor to the head of the
         * related protocol list, eventually creating such head if not already
         * there.
         */
        if (!phead) {
                phead = kzalloc_obj(*phead);
                if (!phead) {
                        kfree(rdev);
                        ret = -ENOMEM;
                        goto out;
                }
                INIT_LIST_HEAD(phead);

                ret = idr_alloc(&scmi_requested_devices, (void *)phead,
                                id_table->protocol_id,
                                id_table->protocol_id + 1, GFP_KERNEL);
                if (ret != id_table->protocol_id) {
                        pr_err("Failed to save SCMI device - ret:%d\n", ret);
                        kfree(rdev);
                        kfree(phead);
                        ret = -EINVAL;
                        goto out;
                }
                ret = 0;
        }
        list_add(&rdev->node, phead);

out:
        mutex_unlock(&scmi_requested_devices_mtx);

        if (!ret)
                blocking_notifier_call_chain(&scmi_requested_devices_nh,
                                             SCMI_BUS_NOTIFY_DEVICE_REQUEST,
                                             (void *)rdev->id_table);

        return ret;
}

static int scmi_protocol_table_register(const struct scmi_device_id *id_table)
{
        int ret = 0;
        const struct scmi_device_id *entry;

        for (entry = id_table; entry->name && ret == 0; entry++)
                ret = scmi_protocol_device_request(entry);

        return ret;
}

/**
 * scmi_protocol_device_unrequest  - Helper to unrequest a device
 *
 * @id_table: A protocol/name pair descriptor for the device to be unrequested.
 *
 * The unrequested device, described by the provided id_table, is at first
 * removed from the IDR @scmi_requested_devices and then the removal is
 * advertised to any registered party via the @scmi_requested_devices_nh
 * notification chain.
 */
static void scmi_protocol_device_unrequest(const struct scmi_device_id *id_table)
{
        struct list_head *phead;

        pr_debug("Unrequesting SCMI device (%s) for protocol %x\n",
                 id_table->name, id_table->protocol_id);

        mutex_lock(&scmi_requested_devices_mtx);
        phead = idr_find(&scmi_requested_devices, id_table->protocol_id);
        if (phead) {
                struct scmi_requested_dev *victim, *tmp;

                list_for_each_entry_safe(victim, tmp, phead, node) {
                        if (!strcmp(victim->id_table->name, id_table->name)) {
                                list_del(&victim->node);

                                mutex_unlock(&scmi_requested_devices_mtx);
                                blocking_notifier_call_chain(&scmi_requested_devices_nh,
                                                             SCMI_BUS_NOTIFY_DEVICE_UNREQUEST,
                                                             (void *)victim->id_table);
                                kfree(victim);
                                mutex_lock(&scmi_requested_devices_mtx);
                                break;
                        }
                }

                if (list_empty(phead)) {
                        idr_remove(&scmi_requested_devices,
                                   id_table->protocol_id);
                        kfree(phead);
                }
        }
        mutex_unlock(&scmi_requested_devices_mtx);
}

static void
scmi_protocol_table_unregister(const struct scmi_device_id *id_table)
{
        const struct scmi_device_id *entry;

        for (entry = id_table; entry->name; entry++)
                scmi_protocol_device_unrequest(entry);
}

static int scmi_dev_match_by_id_table(struct scmi_device *scmi_dev,
                                      const struct scmi_device_id *id_table)
{
        if (!id_table || !id_table->name)
                return 0;

        /* Always skip transport devices from matching */
        for (; id_table->protocol_id && id_table->name; id_table++)
                if (id_table->protocol_id == scmi_dev->protocol_id &&
                    strncmp(scmi_dev->name, "__scmi_transport_device", 23) &&
                    !strcmp(id_table->name, scmi_dev->name))
                        return 1;
        return 0;
}

static int scmi_dev_match_id(struct scmi_device *scmi_dev,
                             const struct scmi_driver *scmi_drv)
{
        return scmi_dev_match_by_id_table(scmi_dev, scmi_drv->id_table);
}

static int scmi_dev_match(struct device *dev, const struct device_driver *drv)
{
        const struct scmi_driver *scmi_drv = to_scmi_driver(drv);
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        return scmi_dev_match_id(scmi_dev, scmi_drv);
}

static int scmi_match_by_id_table(struct device *dev, const void *data)
{
        struct scmi_device *scmi_dev = to_scmi_dev(dev);
        const struct scmi_device_id *id_table = data;

        return scmi_dev_match_by_id_table(scmi_dev, id_table);
}

static struct scmi_device *scmi_child_dev_find(struct device *parent,
                                               int prot_id, const char *name)
{
        struct scmi_device_id id_table[2] = { 0 };
        struct device *dev;

        id_table[0].protocol_id = prot_id;
        id_table[0].name = name;

        dev = device_find_child(parent, &id_table, scmi_match_by_id_table);
        if (!dev)
                return NULL;

        /* Drop the refcnt bumped implicitly by device_find_child */
        put_device(dev);

        return to_scmi_dev(dev);
}

static int scmi_dev_probe(struct device *dev)
{
        struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        if (!scmi_dev->handle)
                return -EPROBE_DEFER;

        return scmi_drv->probe(scmi_dev);
}

static void scmi_dev_remove(struct device *dev)
{
        struct scmi_driver *scmi_drv = to_scmi_driver(dev->driver);
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        if (scmi_drv->remove)
                scmi_drv->remove(scmi_dev);
}

static int scmi_device_uevent(const struct device *dev, struct kobj_uevent_env *env)
{
        const struct scmi_device *scmi_dev = to_scmi_dev(dev);

        return add_uevent_var(env, "MODALIAS=" SCMI_UEVENT_MODALIAS_FMT,
                              dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
                              scmi_dev->name);
}

static ssize_t modalias_show(struct device *dev,
                             struct device_attribute *attr, char *buf)
{
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        return sysfs_emit(buf, SCMI_UEVENT_MODALIAS_FMT,
                          dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
                          scmi_dev->name);
}
static DEVICE_ATTR_RO(modalias);

static ssize_t protocol_id_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        return sprintf(buf, "0x%02x\n", scmi_dev->protocol_id);
}
static DEVICE_ATTR_RO(protocol_id);

static ssize_t name_show(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        return sprintf(buf, "%s\n", scmi_dev->name);
}
static DEVICE_ATTR_RO(name);

static struct attribute *scmi_device_attributes_attrs[] = {
        &dev_attr_protocol_id.attr,
        &dev_attr_name.attr,
        &dev_attr_modalias.attr,
        NULL,
};
ATTRIBUTE_GROUPS(scmi_device_attributes);

static int scmi_pm_suspend(struct device *dev)
{
        const struct device_driver *drv = dev->driver;

        if (drv && drv->pm && drv->pm->suspend)
                return drv->pm->suspend(dev);

        return 0;
}

static int scmi_pm_resume(struct device *dev)
{
        const struct device_driver *drv = dev->driver;

        if (drv && drv->pm && drv->pm->resume)
                return drv->pm->resume(dev);

        return 0;
}

static const struct dev_pm_ops scmi_dev_pm_ops = {
        .suspend = pm_sleep_ptr(scmi_pm_suspend),
        .resume = pm_sleep_ptr(scmi_pm_resume),
};

const struct bus_type scmi_bus_type = {
        .name = "scmi_protocol",
        .match = scmi_dev_match,
        .probe = scmi_dev_probe,
        .remove = scmi_dev_remove,
        .uevent = scmi_device_uevent,
        .dev_groups = scmi_device_attributes_groups,
        .pm = &scmi_dev_pm_ops,
};
EXPORT_SYMBOL_GPL(scmi_bus_type);

int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
                         const char *mod_name)
{
        int retval;

        if (!driver->probe)
                return -EINVAL;

        retval = scmi_protocol_table_register(driver->id_table);
        if (retval)
                return retval;

        driver->driver.bus = &scmi_bus_type;
        driver->driver.name = driver->name;
        driver->driver.owner = owner;
        driver->driver.mod_name = mod_name;

        retval = driver_register(&driver->driver);
        if (!retval)
                pr_debug("Registered new scmi driver %s\n", driver->name);

        return retval;
}
EXPORT_SYMBOL_GPL(scmi_driver_register);

void scmi_driver_unregister(struct scmi_driver *driver)
{
        driver_unregister(&driver->driver);
        scmi_protocol_table_unregister(driver->id_table);
}
EXPORT_SYMBOL_GPL(scmi_driver_unregister);

static void scmi_device_release(struct device *dev)
{
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        kfree_const(scmi_dev->name);
        kfree(scmi_dev);
}

static void __scmi_device_destroy(struct scmi_device *scmi_dev)
{
        pr_debug("(%pOF) Destroying SCMI device '%s' for protocol 0x%x (%s)\n",
                 scmi_dev->dev.parent->of_node,
                 dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
                 scmi_dev->name);

        if (scmi_dev->protocol_id == SCMI_PROTOCOL_SYSTEM)
                atomic_set(&scmi_syspower_registered, 0);

        ida_free(&scmi_bus_id, scmi_dev->id);
        device_unregister(&scmi_dev->dev);
}

static struct scmi_device *
__scmi_device_create(struct device_node *np, struct device *parent,
                     int protocol, const char *name)
{
        int id, retval;
        struct scmi_device *scmi_dev;

        /*
         * If the same protocol/name device already exist under the same parent
         * (i.e. SCMI instance) just return the existent device.
         * This avoids any race between the SCMI driver, creating devices for
         * each DT defined protocol at probe time, and the concurrent
         * registration of SCMI drivers.
         */
        scmi_dev = scmi_child_dev_find(parent, protocol, name);
        if (scmi_dev)
                return scmi_dev;

        /*
         * Ignore any possible subsequent failures while creating the device
         * since we are doomed anyway at that point; not using a mutex which
         * spans across this whole function to keep things simple and to avoid
         * to serialize all the __scmi_device_create calls across possibly
         * different SCMI server instances (parent)
         */
        if (protocol == SCMI_PROTOCOL_SYSTEM &&
            atomic_cmpxchg(&scmi_syspower_registered, 0, 1)) {
                dev_warn(parent,
                         "SCMI SystemPower protocol device must be unique !\n");
                return NULL;
        }

        scmi_dev = kzalloc_obj(*scmi_dev);
        if (!scmi_dev)
                return NULL;

        scmi_dev->name = kstrdup_const(name ?: "unknown", GFP_KERNEL);
        if (!scmi_dev->name) {
                kfree(scmi_dev);
                return NULL;
        }

        id = ida_alloc_min(&scmi_bus_id, 1, GFP_KERNEL);
        if (id < 0) {
                kfree_const(scmi_dev->name);
                kfree(scmi_dev);
                return NULL;
        }

        scmi_dev->id = id;
        scmi_dev->protocol_id = protocol;
        scmi_dev->dev.parent = parent;
        device_set_node(&scmi_dev->dev, of_fwnode_handle(np));
        scmi_dev->dev.bus = &scmi_bus_type;
        scmi_dev->dev.release = scmi_device_release;
        dev_set_name(&scmi_dev->dev, "scmi_dev.%d", id);

        retval = device_register(&scmi_dev->dev);
        if (retval)
                goto put_dev;

        pr_debug("(%pOF) Created SCMI device '%s' for protocol 0x%x (%s)\n",
                 parent->of_node, dev_name(&scmi_dev->dev), protocol, name);

        return scmi_dev;
put_dev:
        put_device(&scmi_dev->dev);
        ida_free(&scmi_bus_id, id);
        return NULL;
}

static struct scmi_device *
_scmi_device_create(struct device_node *np, struct device *parent,
                    int protocol, const char *name)
{
        struct scmi_device *sdev;

        sdev = __scmi_device_create(np, parent, protocol, name);
        if (!sdev)
                pr_err("(%pOF) Failed to create device for protocol 0x%x (%s)\n",
                       parent->of_node, protocol, name);

        return sdev;
}

/**
 * scmi_device_create  - A method to create one or more SCMI devices
 *
 * @np: A reference to the device node to use for the new device(s)
 * @parent: The parent device to use identifying a specific SCMI instance
 * @protocol: The SCMI protocol to be associated with this device
 * @name: The requested-name of the device to be created; this is optional
 *        and if no @name is provided, all the devices currently known to
 *        be requested on the SCMI bus for @protocol will be created.
 *
 * This method can be invoked to create a single well-defined device (like
 * a transport device or a device requested by an SCMI driver loaded after
 * the core SCMI stack has been probed), or to create all the devices currently
 * known to have been requested by the loaded SCMI drivers for a specific
 * protocol (typically during SCMI core protocol enumeration at probe time).
 *
 * Return: The created device (or one of them if @name was NOT provided and
 *         multiple devices were created) or NULL if no device was created;
 *         note that NULL indicates an error ONLY in case a specific @name
 *         was provided: when @name param was not provided, a number of devices
 *         could have been potentially created for a whole protocol, unless no
 *         device was found to have been requested for that specific protocol.
 */
struct scmi_device *scmi_device_create(struct device_node *np,
                                       struct device *parent, int protocol,
                                       const char *name)
{
        struct list_head *phead;
        struct scmi_requested_dev *rdev;
        struct scmi_device *scmi_dev = NULL;

        if (name)
                return _scmi_device_create(np, parent, protocol, name);

        mutex_lock(&scmi_requested_devices_mtx);
        phead = idr_find(&scmi_requested_devices, protocol);
        /* Nothing to do. */
        if (!phead) {
                mutex_unlock(&scmi_requested_devices_mtx);
                return NULL;
        }

        /* Walk the list of requested devices for protocol and create them */
        list_for_each_entry(rdev, phead, node) {
                struct scmi_device *sdev;

                sdev = _scmi_device_create(np, parent,
                                           rdev->id_table->protocol_id,
                                           rdev->id_table->name);
                if (sdev)
                        scmi_dev = sdev;
        }

        mutex_unlock(&scmi_requested_devices_mtx);

        return scmi_dev;
}
EXPORT_SYMBOL_GPL(scmi_device_create);

void scmi_device_destroy(struct device *parent, int protocol, const char *name)
{
        struct scmi_device *scmi_dev;

        scmi_dev = scmi_child_dev_find(parent, protocol, name);
        if (scmi_dev)
                __scmi_device_destroy(scmi_dev);
}
EXPORT_SYMBOL_GPL(scmi_device_destroy);

static int __scmi_devices_unregister(struct device *dev, void *data)
{
        struct scmi_device *scmi_dev = to_scmi_dev(dev);

        __scmi_device_destroy(scmi_dev);
        return 0;
}

static void scmi_devices_unregister(void)
{
        bus_for_each_dev(&scmi_bus_type, NULL, NULL, __scmi_devices_unregister);
}

static int __init scmi_bus_init(void)
{
        int retval;

        retval = bus_register(&scmi_bus_type);
        if (retval)
                pr_err("SCMI protocol bus register failed (%d)\n", retval);

        pr_info("SCMI protocol bus registered\n");

        return retval;
}
subsys_initcall(scmi_bus_init);

static void __exit scmi_bus_exit(void)
{
        /*
         * Destroy all remaining devices: just in case the drivers were
         * manually unbound and at first and then the modules unloaded.
         */
        scmi_devices_unregister();
        bus_unregister(&scmi_bus_type);
        ida_destroy(&scmi_bus_id);
}
module_exit(scmi_bus_exit);

MODULE_ALIAS("scmi-core");
MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
MODULE_DESCRIPTION("ARM SCMI protocol bus");
MODULE_LICENSE("GPL");