// SPDX-License-Identifier: GPL-2.0
/*
 * driver.c - centralized device driver management
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 * Copyright (c) 2007 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (c) 2007 Novell Inc.
 */

#include <linux/device/driver.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include "base.h"

static struct device *next_device(struct klist_iter *i)
{
        struct klist_node *n = klist_next(i);
        struct device *dev = NULL;
        struct device_private *dev_prv;

        if (n) {
                dev_prv = to_device_private_driver(n);
                dev = dev_prv->device;
        }
        return dev;
}

/**
 * driver_set_override() - Helper to set or clear driver override.
 * @dev: Device to change
 * @override: Address of string to change (e.g. &device->driver_override);
 *            The contents will be freed and hold newly allocated override.
 * @s: NUL-terminated string, new driver name to force a match, pass empty
 *     string to clear it ("" or "\n", where the latter is only for sysfs
 *     interface).
 * @len: length of @s
 *
 * Helper to set or clear driver override in a device, intended for the cases
 * when the driver_override field is allocated by driver/bus code.
 *
 * Returns: 0 on success or a negative error code on failure.
 */
int driver_set_override(struct device *dev, const char **override,
                        const char *s, size_t len)
{
        const char *new, *old;
        char *cp;

        if (!override || !s)
                return -EINVAL;

        /*
         * The stored value will be used in sysfs show callback (sysfs_emit()),
         * which has a length limit of PAGE_SIZE and adds a trailing newline.
         * Thus we can store one character less to avoid truncation during sysfs
         * show.
         */
        if (len >= (PAGE_SIZE - 1))
                return -EINVAL;

        /*
         * Compute the real length of the string in case userspace sends us a
         * bunch of \0 characters like python likes to do.
         */
        len = strlen(s);

        if (!len) {
                /* Empty string passed - clear override */
                device_lock(dev);
                old = *override;
                *override = NULL;
                device_unlock(dev);
                kfree(old);

                return 0;
        }

        cp = strnchr(s, len, '\n');
        if (cp)
                len = cp - s;

        new = kstrndup(s, len, GFP_KERNEL);
        if (!new)
                return -ENOMEM;

        device_lock(dev);
        old = *override;
        if (cp != s) {
                *override = new;
        } else {
                /* "\n" passed - clear override */
                kfree(new);
                *override = NULL;
        }
        device_unlock(dev);

        kfree(old);

        return 0;
}
EXPORT_SYMBOL_GPL(driver_set_override);

/**
 * driver_for_each_device - Iterator for devices bound to a driver.
 * @drv: Driver we're iterating.
 * @start: Device to begin with
 * @data: Data to pass to the callback.
 * @fn: Function to call for each device.
 *
 * Iterate over the @drv's list of devices calling @fn for each one.
 */
int driver_for_each_device(struct device_driver *drv, struct device *start,
                           void *data, device_iter_t fn)
{
        struct klist_iter i;
        struct device *dev;
        int error = 0;

        if (!drv)
                return -EINVAL;

        klist_iter_init_node(&drv->p->klist_devices, &i,
                             start ? &start->p->knode_driver : NULL);
        while (!error && (dev = next_device(&i)))
                error = fn(dev, data);
        klist_iter_exit(&i);
        return error;
}
EXPORT_SYMBOL_GPL(driver_for_each_device);

/**
 * driver_find_device - device iterator for locating a particular device.
 * @drv: The device's driver
 * @start: Device to begin with
 * @data: Data to pass to match function
 * @match: Callback function to check device
 *
 * This is similar to the driver_for_each_device() function above, but
 * it returns a reference to a device that is 'found' for later use, as
 * determined by the @match callback.
 *
 * The callback should return 0 if the device doesn't match and non-zero
 * if it does.  If the callback returns non-zero, this function will
 * return to the caller and not iterate over any more devices.
 */
struct device *driver_find_device(const struct device_driver *drv,
                                  struct device *start, const void *data,
                                  device_match_t match)
{
        struct klist_iter i;
        struct device *dev;

        if (!drv || !drv->p)
                return NULL;

        klist_iter_init_node(&drv->p->klist_devices, &i,
                             (start ? &start->p->knode_driver : NULL));
        while ((dev = next_device(&i))) {
                if (match(dev, data)) {
                        get_device(dev);
                        break;
                }
        }
        klist_iter_exit(&i);
        return dev;
}
EXPORT_SYMBOL_GPL(driver_find_device);

/**
 * driver_create_file - create sysfs file for driver.
 * @drv: driver.
 * @attr: driver attribute descriptor.
 */
int driver_create_file(const struct device_driver *drv,
                       const struct driver_attribute *attr)
{
        int error;

        if (drv)
                error = sysfs_create_file(&drv->p->kobj, &attr->attr);
        else
                error = -EINVAL;
        return error;
}
EXPORT_SYMBOL_GPL(driver_create_file);

/**
 * driver_remove_file - remove sysfs file for driver.
 * @drv: driver.
 * @attr: driver attribute descriptor.
 */
void driver_remove_file(const struct device_driver *drv,
                        const struct driver_attribute *attr)
{
        if (drv)
                sysfs_remove_file(&drv->p->kobj, &attr->attr);
}
EXPORT_SYMBOL_GPL(driver_remove_file);

int driver_add_groups(const struct device_driver *drv,
                      const struct attribute_group **groups)
{
        return sysfs_create_groups(&drv->p->kobj, groups);
}

void driver_remove_groups(const struct device_driver *drv,
                          const struct attribute_group **groups)
{
        sysfs_remove_groups(&drv->p->kobj, groups);
}

/**
 * driver_register - register driver with bus
 * @drv: driver to register
 *
 * We pass off most of the work to the bus_add_driver() call,
 * since most of the things we have to do deal with the bus
 * structures.
 */
int driver_register(struct device_driver *drv)
{
        int ret;
        struct device_driver *other;

        if (!bus_is_registered(drv->bus)) {
                pr_err("Driver '%s' was unable to register with bus_type '%s' because the bus was not initialized.\n",
                           drv->name, drv->bus->name);
                return -EINVAL;
        }

        if ((drv->bus->probe && drv->probe) ||
            (drv->bus->remove && drv->remove) ||
            (drv->bus->shutdown && drv->shutdown))
                pr_warn("Driver '%s' needs updating - please use "
                        "bus_type methods\n", drv->name);

        other = driver_find(drv->name, drv->bus);
        if (other) {
                pr_err("Error: Driver '%s' is already registered, "
                        "aborting...\n", drv->name);
                return -EBUSY;
        }

        ret = bus_add_driver(drv);
        if (ret)
                return ret;
        ret = driver_add_groups(drv, drv->groups);
        if (ret) {
                bus_remove_driver(drv);
                return ret;
        }
        kobject_uevent(&drv->p->kobj, KOBJ_ADD);
        deferred_probe_extend_timeout();

        return ret;
}
EXPORT_SYMBOL_GPL(driver_register);

/**
 * driver_unregister - remove driver from system.
 * @drv: driver.
 *
 * Again, we pass off most of the work to the bus-level call.
 */
void driver_unregister(struct device_driver *drv)
{
        if (!drv || !drv->p) {
                WARN(1, "Unexpected driver unregister!\n");
                return;
        }
        driver_remove_groups(drv, drv->groups);
        bus_remove_driver(drv);
}
EXPORT_SYMBOL_GPL(driver_unregister);