// SPDX-License-Identifier: GPL-2.0
/*
 *  bus driver for ccwgroup
 *
 *  Copyright IBM Corp. 2002, 2012
 *
 *  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/cio.h>
#include <asm/ccwdev.h>
#include <asm/ccwgroup.h>

#include "device.h"

#define CCW_BUS_ID_SIZE         10

/* 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.
 */

static struct bus_type ccwgroup_bus_type;

static void __ccwgroup_remove_symlinks(struct ccwgroup_device *gdev)
{
        int i;
        char str[16];

        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");
        }
}

/*
 * Remove references from ccw devices to ccw group device and from
 * ccw group device to ccw devices.
 */
static void __ccwgroup_remove_cdev_refs(struct ccwgroup_device *gdev)
{
        struct ccw_device *cdev;
        int i;

        for (i = 0; i < gdev->count; i++) {
                cdev = gdev->cdev[i];
                if (!cdev)
                        continue;
                spin_lock_irq(cdev->ccwlock);
                dev_set_drvdata(&cdev->dev, NULL);
                spin_unlock_irq(cdev->ccwlock);
                gdev->cdev[i] = NULL;
                put_device(&cdev->dev);
        }
}

/**
 * ccwgroup_set_online() - enable a ccwgroup device
 * @gdev: target ccwgroup device
 *
 * This function attempts to put the ccwgroup device into the online state.
 * Returns:
 *  %0 on success and a negative error value on failure.
 */
int ccwgroup_set_online(struct ccwgroup_device *gdev)
{
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);
        int ret = -EINVAL;

        if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
                return -EAGAIN;
        if (gdev->state == CCWGROUP_ONLINE)
                goto out;
        if (gdrv->set_online)
                ret = gdrv->set_online(gdev);
        if (ret)
                goto out;

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

/**
 * ccwgroup_set_offline() - disable a ccwgroup device
 * @gdev: target ccwgroup device
 *
 * This function attempts to put the ccwgroup device into the offline state.
 * Returns:
 *  %0 on success and a negative error value on failure.
 */
int ccwgroup_set_offline(struct ccwgroup_device *gdev)
{
        struct ccwgroup_driver *gdrv = to_ccwgroupdrv(gdev->dev.driver);
        int ret = -EINVAL;

        if (atomic_cmpxchg(&gdev->onoff, 0, 1) != 0)
                return -EAGAIN;
        if (gdev->state == CCWGROUP_OFFLINE)
                goto out;
        if (gdrv->set_offline)
                ret = gdrv->set_offline(gdev);
        if (ret)
                goto out;

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

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

        device_lock(dev);
        if (!dev->driver) {
                ret = -EINVAL;
                goto out;
        }

        ret = kstrtoul(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:
        device_unlock(dev);
        return (ret == 0) ? count : ret;
}

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

        online = (gdev->state == CCWGROUP_ONLINE) ? 1 : 0;

        return scnprintf(buf, PAGE_SIZE, "%d\n", online);
}

/*
 * Provide an 'ungroup' attribute so the user can remove group devices no
 * longer needed or accidentially created. Saves memory :)
 */
static void ccwgroup_ungroup(struct ccwgroup_device *gdev)
{
        mutex_lock(&gdev->reg_mutex);
        if (device_is_registered(&gdev->dev)) {
                __ccwgroup_remove_symlinks(gdev);
                device_unregister(&gdev->dev);
                __ccwgroup_remove_cdev_refs(gdev);
        }
        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 = to_ccwgroupdev(dev);
        int rc = 0;

        /* 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;
        }

        if (device_remove_file_self(dev, attr))
                ccwgroup_ungroup(gdev);
        else
                rc = -ENODEV;
out:
        if (rc) {
                /* 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 DEVICE_ATTR(online, 0644, ccwgroup_online_show, ccwgroup_online_store);

static struct attribute *ccwgroup_attrs[] = {
        &dev_attr_online.attr,
        &dev_attr_ungroup.attr,
        NULL,
};
static struct attribute_group ccwgroup_attr_group = {
        .attrs = ccwgroup_attrs,
};
static const struct attribute_group *ccwgroup_attr_groups[] = {
        &ccwgroup_attr_group,
        NULL,
};

static void ccwgroup_ungroup_workfn(struct work_struct *work)
{
        struct ccwgroup_device *gdev =
                container_of(work, struct ccwgroup_device, ungroup_work);

        ccwgroup_ungroup(gdev);
        put_device(&gdev->dev);
}

static void ccwgroup_release(struct device *dev)
{
        kfree(to_ccwgroupdev(dev));
}

static int __ccwgroup_create_symlinks(struct ccwgroup_device *gdev)
{
        char str[16];
        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_id(const char **buf, struct ccw_dev_id *id)
{
        unsigned int cssid, ssid, devno;
        int ret = 0, 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) {
                if (sscanf(start, "%2x.%1x.%04x", &cssid, &ssid, &devno) != 3)
                        ret = -EINVAL;
        } else
                ret = -EINVAL;

        if (!ret) {
                id->ssid = ssid;
                id->devno = devno;
        }
        *buf = end;
        return ret;
}

/**
 * ccwgroup_create_dev() - create and register a ccw group device
 * @parent: parent device for the new device
 * @gdrv: driver for the new group device
 * @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 @parent. Slave
 * devices are obtained from the list of bus ids given in @buf.
 * Returns:
 *  %0 on success and an error code on failure.
 * Context:
 *  non-atomic
 */
int ccwgroup_create_dev(struct device *parent, struct ccwgroup_driver *gdrv,
                        int num_devices, const char *buf)
{
        struct ccwgroup_device *gdev;
        struct ccw_dev_id dev_id;
        int rc, i;

        if (num_devices < 1)
                return -EINVAL;

        gdev = kzalloc(struct_size(gdev, cdev, num_devices), GFP_KERNEL);
        if (!gdev)
                return -ENOMEM;

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

        for (i = 0; i < num_devices && buf; i++) {
                rc = __get_next_id(&buf, &dev_id);
                if (rc != 0)
                        goto error;
                gdev->cdev[i] = get_ccwdev_by_dev_id(&dev_id);
                /*
                 * All devices have to be of the same type in
                 * order to be grouped.
                 */
                if (!gdev->cdev[i] || !gdev->cdev[i]->drv ||
                    gdev->cdev[i]->drv != gdev->cdev[0]->drv ||
                    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. */
                spin_lock_irq(gdev->cdev[i]->ccwlock);
                if (dev_get_drvdata(&gdev->cdev[i]->dev)) {
                        spin_unlock_irq(gdev->cdev[i]->ccwlock);
                        rc = -EINVAL;
                        goto error;
                }
                dev_set_drvdata(&gdev->cdev[i]->dev, gdev);
                spin_unlock_irq(gdev->cdev[i]->ccwlock);
        }
        /* Check for sufficient number of bus ids. */
        if (i < num_devices) {
                rc = -EINVAL;
                goto error;
        }
        /* Check for trailing stuff. */
        if (i == num_devices && buf && strlen(buf) > 0) {
                rc = -EINVAL;
                goto error;
        }
        /* Check if the devices are bound to the required ccw driver. */
        if (gdrv && gdrv->ccw_driver &&
            gdev->cdev[0]->drv != gdrv->ccw_driver) {
                rc = -EINVAL;
                goto error;
        }

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

        if (gdrv) {
                gdev->dev.driver = &gdrv->driver;
                rc = gdrv->setup ? gdrv->setup(gdev) : 0;
                if (rc)
                        goto error;
        }
        rc = device_add(&gdev->dev);
        if (rc)
                goto error;
        rc = __ccwgroup_create_symlinks(gdev);
        if (rc) {
                device_del(&gdev->dev);
                goto error;
        }
        mutex_unlock(&gdev->reg_mutex);
        return 0;
error:
        for (i = 0; i < num_devices; i++)
                if (gdev->cdev[i]) {
                        spin_lock_irq(gdev->cdev[i]->ccwlock);
                        if (dev_get_drvdata(&gdev->cdev[i]->dev) == gdev)
                                dev_set_drvdata(&gdev->cdev[i]->dev, NULL);
                        spin_unlock_irq(gdev->cdev[i]->ccwlock);
                        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_dev);

static int ccwgroup_notifier(struct notifier_block *nb, unsigned long action,
                             void *data)
{
        struct ccwgroup_device *gdev = to_ccwgroupdev(data);

        if (action == BUS_NOTIFY_UNBIND_DRIVER) {
                get_device(&gdev->dev);
                schedule_work(&gdev->ungroup_work);
        }

        return NOTIFY_OK;
}

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

        if (!dev->driver)
                return 0;
        if (gdrv->remove)
                gdrv->remove(gdev);

        return 0;
}

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

        if (!dev->driver)
                return;
        if (gdrv->shutdown)
                gdrv->shutdown(gdev);
}

static struct bus_type ccwgroup_bus_type = {
        .name   = "ccwgroup",
        .remove = ccwgroup_remove,
        .shutdown = ccwgroup_shutdown,
};

bool dev_is_ccwgroup(struct device *dev)
{
        return dev->bus == &ccwgroup_bus_type;
}
EXPORT_SYMBOL(dev_is_ccwgroup);

/**
 * 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;

        return driver_register(&cdriver->driver);
}
EXPORT_SYMBOL(ccwgroup_driver_register);

/**
 * 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. */
        while ((dev = driver_find_next_device(&cdriver->driver, NULL))) {
                struct ccwgroup_device *gdev = to_ccwgroupdev(dev);

                ccwgroup_ungroup(gdev);
                put_device(dev);
        }
        driver_unregister(&cdriver->driver);
}
EXPORT_SYMBOL(ccwgroup_driver_unregister);

/**
 * get_ccwgroupdev_by_busid() - obtain device from a bus id
 * @gdrv: driver the device is owned by
 * @bus_id: bus id of the device to be searched
 *
 * This function searches all devices owned by @gdrv for a device with a bus
 * id matching @bus_id.
 * Returns:
 *  If a match is found, its reference count of the found device is increased
 *  and it is returned; else %NULL is returned.
 */
struct ccwgroup_device *get_ccwgroupdev_by_busid(struct ccwgroup_driver *gdrv,
                                                 char *bus_id)
{
        struct device *dev;

        dev = driver_find_device_by_name(&gdrv->driver, bus_id);

        return dev ? to_ccwgroupdev(dev) : NULL;
}
EXPORT_SYMBOL_GPL(get_ccwgroupdev_by_busid);

/**
 * 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;
}
EXPORT_SYMBOL(ccwgroup_probe_ccwdev);

/**
 * 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. */
        spin_lock_irq(cdev->ccwlock);
        gdev = dev_get_drvdata(&cdev->dev);
        if (!gdev) {
                spin_unlock_irq(cdev->ccwlock);
                return;
        }
        /* Get ccwgroup device reference for local processing. */
        get_device(&gdev->dev);
        spin_unlock_irq(cdev->ccwlock);
        /* Unregister group device. */
        ccwgroup_ungroup(gdev);
        /* Release ccwgroup device reference for local processing. */
        put_device(&gdev->dev);
}
EXPORT_SYMBOL(ccwgroup_remove_ccwdev);
MODULE_LICENSE("GPL");