source: mainline/uspace/srv/devman/driver.c@ e55741e

/*
 * Copyright (c) 2018 Jiri Svoboda
 * Copyright (c) 2010 Lenka Trochtova
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup devman
 * @{
 */

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <io/log.h>
#include <vfs/vfs.h>
#include <loc.h>
#include <stdio.h>
#include <str_error.h>
#include <sys/stat.h>
#include <sysman/ctl.h>
#include <task.h>

#include "dev.h"
#include "devman.h"
#include "driver.h"
#include "fun.h"
#include "match.h"
#include "main.h"

static errno_t driver_reassign_fibril(void *);

/**
 * Initialize the list of device driver's.
 *
 * @param drv_list the list of device driver's.
 *
 */
void init_driver_list(driver_list_t *drv_list)
{
        assert(drv_list != NULL);

        list_initialize(&drv_list->drivers);
        fibril_mutex_initialize(&drv_list->drivers_mutex);
        drv_list->next_handle = 1;
}

/** Allocate and initialize a new driver structure.
 *
 * @return      Driver structure.
 */
driver_t *create_driver(void)
{
        driver_t *res = malloc(sizeof(driver_t));
        if (res != NULL)
                init_driver(res);
        return res;
}

/** Add a driver to the list of drivers.
 *
 * @param drivers_list  List of drivers.
 * @param drv           Driver structure.
 */
void add_driver(driver_list_t *drivers_list, driver_t *drv)
{
        fibril_mutex_lock(&drivers_list->drivers_mutex);
        list_append(&drv->drivers, &drivers_list->drivers);
        drv->handle = drivers_list->next_handle++;
        fibril_mutex_unlock(&drivers_list->drivers_mutex);

        log_msg(LOG_DEFAULT, LVL_DEBUG, "Driver `%s' was added to the list of available "
            "drivers.", drv->name);
}

/**
 * Get information about a driver.
 *
 * Each driver has its own directory in the base directory.
 * The name of the driver's directory is the same as the name of the driver.
 * The driver's directory contains driver's binary (named as the driver without
 * extension) and the configuration file with match ids for device-to-driver
 *  matching (named as the driver with a special extension).
 *
 * This function searches for the driver's directory and containing
 * configuration files. If all the files needed are found, they are parsed and
 * the information about the driver is stored in the driver's structure.
 *
 * @param base_path     The base directory, in which we look for driver's
 *                      subdirectory.
 * @param name          The name of the driver.
 * @param drv           The driver structure to fill information in.
 *
 * @return              True on success, false otherwise.
 */
bool get_driver_info(const char *base_path, const char *name, driver_t *drv)
{
        log_msg(LOG_DEFAULT, LVL_DEBUG, "get_driver_info(base_path=\"%s\", name=\"%s\")",
            base_path, name);

        assert(base_path != NULL && name != NULL && drv != NULL);

        bool suc = false;
        char *match_path = NULL;
        size_t name_size = 0;

        /* Read the list of match ids from the driver's configuration file. */
        match_path = get_abs_path(base_path, name, MATCH_EXT);
        if (match_path == NULL)
                goto cleanup;

        if (!read_match_ids(match_path, &drv->match_ids))
                goto cleanup;

        /* Allocate and fill driver's name. */
        name_size = str_size(name) + 1;
        drv->name = malloc(name_size);
        if (drv->name == NULL)
                goto cleanup;
        str_cpy(drv->name, name_size, name);

        suc = true;

cleanup:
        if (!suc) {
                free(drv->name);
                /* Set the driver structure to the default state. */
                init_driver(drv);
        }

        free(match_path);

        return suc;
}

/** Lookup drivers in the directory.
 *
 * @param drivers_list  The list of available drivers.
 * @param dir_path      The path to the directory where we search for drivers.
 * @return              Number of drivers which were found.
 */
int lookup_available_drivers(driver_list_t *drivers_list, const char *dir_path)
{
        log_msg(LOG_DEFAULT, LVL_DEBUG, "lookup_available_drivers(dir=\"%s\")", dir_path);

        int drv_cnt = 0;
        DIR *dir = NULL;
        struct dirent *diren;

        dir = opendir(dir_path);

        if (dir != NULL) {
                driver_t *drv = create_driver();
                while ((diren = readdir(dir))) {
                        if (get_driver_info(dir_path, diren->d_name, drv)) {
                                add_driver(drivers_list, drv);
                                drv_cnt++;
                                drv = create_driver();
                        }
                }
                delete_driver(drv);
                closedir(dir);
        }

        return drv_cnt;
}

/** Lookup the next best matching driver for a device.
 *
 * A match between a device and a driver is found if one of the driver's match
 * ids match one of the device's match ids. The score of the match is the
 * product of the driver's and device's score associated with the matching id.
 * The best matching driver for a device is the driver with the highest score
 * of the match between the device and the driver.
 *
 * If a driver is already assigned to the device (node->drv != NULL),
 * we look for the next best driver. That is either the next driver with the
 * same score in the list of drivers, or a driver with the next best score
 * (greater than zero).
 *
 * @param drivers_list  The list of drivers, where we look for the driver
 *                      suitable for handling the device.
 * @param node          The device node structure of the device.
 * @return              The best matching driver or NULL if no matching driver
 *                      is found.
 */
driver_t *find_best_match_driver(driver_list_t *drivers_list, dev_node_t *node)
{
        driver_t *best_drv = NULL;
        int best_score = 0, score = 0;
        int cur_score;
        link_t *link;

        fibril_mutex_lock(&drivers_list->drivers_mutex);

        if (node->drv != NULL) {
                cur_score = get_match_score(node->drv, node);

                link = list_next(&node->drv->drivers, &drivers_list->drivers);

                /*
                 * Find next driver with score equal to the current.
                 */
                while (link != NULL) {
                        driver_t *drv = list_get_instance(link, driver_t,
                            drivers);
                        score = get_match_score(drv, node);
                        if (score == cur_score) {
                                /* Found it */
                                fibril_mutex_unlock(&drivers_list->drivers_mutex);
                                return drv;
                        }

                        link = list_next(link, &drivers_list->drivers);
                }

                /* There is no driver with the same score */
        } else {
                cur_score = INT_MAX;
        }

        /*
         * Find driver with the next best score
         */
        list_foreach(drivers_list->drivers, drivers, driver_t, drv) {
                score = get_match_score(drv, node);
                if (score > best_score && score < cur_score) {
                        best_score = score;
                        best_drv = drv;
                }
        }

        fibril_mutex_unlock(&drivers_list->drivers_mutex);
        return best_drv;
}

/** Assign a driver to a device.
 *
 * @param tree          Device tree
 * @param dev           The device's node in the device tree.
 * @param drv           The driver.
 */
void attach_driver(dev_tree_t *tree, dev_node_t *dev, driver_t *drv)
{
        log_msg(LOG_DEFAULT, LVL_DEBUG, "attach_driver(dev=\"%s\",drv=\"%s\")",
            dev->pfun->pathname, drv->name);

        fibril_mutex_lock(&drv->driver_mutex);
        fibril_rwlock_write_lock(&tree->rwlock);

        dev->drv = drv;
        dev->passed_to_driver = false;
        dev->state = DEVICE_NOT_INITIALIZED;
        list_append(&dev->driver_devices, &drv->devices);

        fibril_rwlock_write_unlock(&tree->rwlock);
        fibril_mutex_unlock(&drv->driver_mutex);
}

/** Detach driver from device.
 *
 * @param tree          Device tree
 * @param node          The device's node in the device tree.
 * @param drv           The driver.
 */
void detach_driver(dev_tree_t *tree, dev_node_t *dev)
{
        driver_t *drv = dev->drv;

        assert(drv != NULL);

        log_msg(LOG_DEFAULT, LVL_DEBUG, "detach_driver(dev=\"%s\",drv=\"%s\")",
            dev->pfun->pathname, drv->name);

        fibril_mutex_lock(&drv->driver_mutex);
        fibril_rwlock_write_lock(&tree->rwlock);

        dev->drv = NULL;
        list_remove(&dev->driver_devices);

        fibril_rwlock_write_unlock(&tree->rwlock);
        fibril_mutex_unlock(&drv->driver_mutex);
}

/** Start a driver
 *
 * @param drv           The driver's structure.
 * @return              True if the driver's task is successfully spawned, false
 *                      otherwise.
 */
bool start_driver(driver_t *drv)
{
        errno_t rc;

        assert(fibril_mutex_is_locked(&drv->driver_mutex));

        log_msg(LOG_DEFAULT, LVL_DEBUG, "start_driver(drv=\"%s\")", drv->name);

        char *unit_name = NULL;
        asprintf(&unit_name, "%s%c%s", drv->name, UNIT_NAME_SEPARATOR,
            UNIT_SVC_TYPE_NAME);
        if (unit_name == NULL) {
                return false;
        }

        /*
         * Non-blocking asynchronous request to start a driver
         * FIXME See note about sysman_unit_start non-blocking (asynchronous)
         *       API
         */
        int flags = 0;
        rc = sysman_unit_start(unit_name, flags);

        if (rc != EOK) {
                log_msg(LOG_DEFAULT, LVL_ERROR,
                    "Request to start driver `%s' failed: %s.",
                    drv->name, str_error(rc));
                free(unit_name);
                return false;
        }

        drv->state = DRIVER_STARTING;
        free(unit_name);
        return true;
}

/** Stop a driver
 *
 * @param drv           The driver's structure.
 * @return              True if the driver's task is successfully spawned, false
 *                      otherwise.
 */
errno_t stop_driver(driver_t *drv)
{
        async_exch_t *exch;
        errno_t retval;

        log_msg(LOG_DEFAULT, LVL_DEBUG, "stop_driver(drv=\"%s\")", drv->name);

        exch = async_exchange_begin(drv->sess);
        retval = async_req_0_0(exch, DRIVER_STOP);
        loc_exchange_end(exch);

        if (retval != EOK)
                return retval;

        drv->state = DRIVER_NOT_STARTED;
        async_hangup(drv->sess);
        drv->sess = NULL;
        return EOK;
}

/** Find device driver by handle.
 *
 * @param drv_list      The list of device drivers
 * @param handle        Driver handle
 * @return              The device driver, if it is in the list,
 *                      NULL otherwise.
 */
driver_t *driver_find(driver_list_t *drv_list, devman_handle_t handle)
{
        driver_t *res = NULL;

        fibril_mutex_lock(&drv_list->drivers_mutex);

        list_foreach(drv_list->drivers, drivers, driver_t, drv) {
                if (drv->handle == handle) {
                        res = drv;
                        break;
                }
        }

        fibril_mutex_unlock(&drv_list->drivers_mutex);

        return res;
}

/** Find device driver by name.
 *
 * @param drv_list      The list of device drivers.
 * @param drv_name      The name of the device driver which is searched.
 * @return              The device driver of the specified name, if it is in the
 *                      list, NULL otherwise.
 */
driver_t *driver_find_by_name(driver_list_t *drv_list, const char *drv_name)
{
        driver_t *res = NULL;

        fibril_mutex_lock(&drv_list->drivers_mutex);

        list_foreach(drv_list->drivers, drivers, driver_t, drv) {
                if (str_cmp(drv->name, drv_name) == 0) {
                        res = drv;
                        break;
                }
        }

        fibril_mutex_unlock(&drv_list->drivers_mutex);

        return res;
}

/** Notify driver about the devices to which it was assigned.
 *
 * @param driver        The driver to which the devices are passed.
 */
static void pass_devices_to_driver(driver_t *driver, dev_tree_t *tree)
{
        dev_node_t *dev;
        link_t *link;

        log_msg(LOG_DEFAULT, LVL_DEBUG, "pass_devices_to_driver(driver=\"%s\")",
            driver->name);

        fibril_mutex_lock(&driver->driver_mutex);

        /*
         * Go through devices list as long as there is some device
         * that has not been passed to the driver.
         */
        link = driver->devices.head.next;
        while (link != &driver->devices.head) {
                dev = list_get_instance(link, dev_node_t, driver_devices);
                fibril_rwlock_write_lock(&tree->rwlock);

                if (dev->passed_to_driver) {
                        fibril_rwlock_write_unlock(&tree->rwlock);
                        link = link->next;
                        continue;
                }

                dev_add_ref(dev);

                /*
                 * Unlock to avoid deadlock when adding device
                 * handled by itself.
                 */
                fibril_mutex_unlock(&driver->driver_mutex);
                fibril_rwlock_write_unlock(&tree->rwlock);

                add_device(driver, dev, tree);

                /* Device probe failed, need to try next best driver */
                if (dev->state == DEVICE_NOT_PRESENT) {
                        fibril_mutex_lock(&driver->driver_mutex);
                        list_remove(&dev->driver_devices);
                        fibril_mutex_unlock(&driver->driver_mutex);
                        /* Give an extra reference to driver_reassign_fibril */
                        dev_add_ref(dev);
                        fid_t fid = fibril_create(driver_reassign_fibril, dev);
                        if (fid == 0) {
                                log_msg(LOG_DEFAULT, LVL_ERROR,
                                    "Error creating fibril to assign driver.");
                                dev_del_ref(dev);
                        }
                        fibril_add_ready(fid);
                }

                dev_del_ref(dev);

                /*
                 * Lock again as we will work with driver's
                 * structure.
                 */
                fibril_mutex_lock(&driver->driver_mutex);

                /*
                 * Restart the cycle to go through all devices again.
                 */
                link = driver->devices.head.next;
        }

        /*
         * Once we passed all devices to the driver, we need to mark the
         * driver as running.
         * It is vital to do it here and inside critical section.
         *
         * If we would change the state earlier, other devices added to
         * the driver would be added to the device list and started
         * immediately and possibly started here as well.
         */
        log_msg(LOG_DEFAULT, LVL_DEBUG, "Driver `%s' enters running state.", driver->name);
        driver->state = DRIVER_RUNNING;

        fibril_mutex_unlock(&driver->driver_mutex);
}

/** Finish the initialization of a driver after it has succesfully started
 * and after it has registered itself by the device manager.
 *
 * Pass devices formerly matched to the driver to the driver and remember the
 * driver is running and fully functional now.
 *
 * @param driver        The driver which registered itself as running by the
 *                      device manager.
 */
void initialize_running_driver(driver_t *driver, dev_tree_t *tree)
{
        log_msg(LOG_DEFAULT, LVL_DEBUG, "initialize_running_driver(driver=\"%s\")",
            driver->name);

        /*
         * Pass devices which have been already assigned to the driver to the
         * driver.
         */
        pass_devices_to_driver(driver, tree);
}

/** Initialize device driver structure.
 *
 * @param drv           The device driver structure.
 */
void init_driver(driver_t *drv)
{
        assert(drv != NULL);

        memset(drv, 0, sizeof(driver_t));
        list_initialize(&drv->match_ids.ids);
        list_initialize(&drv->devices);
        fibril_mutex_initialize(&drv->driver_mutex);
        drv->sess = NULL;
}

/** Device driver structure clean-up.
 *
 * @param drv           The device driver structure.
 */
void clean_driver(driver_t *drv)
{
        assert(drv != NULL);

        free(drv->name);

        clean_match_ids(&drv->match_ids);

        init_driver(drv);
}

/** Delete device driver structure.
 *
 * @param drv           The device driver structure.
 */
void delete_driver(driver_t *drv)
{
        assert(drv != NULL);

        clean_driver(drv);
        free(drv);
}

/** Find suitable driver for a device and assign the driver to it.
 *
 * @param dev           The device node of the device in the device tree.
 * @param drivers_list  The list of available drivers.
 * @return              True if the suitable driver is found and
 *                      successfully assigned to the device, false otherwise.
 */
bool assign_driver(dev_node_t *dev, driver_list_t *drivers_list,
    dev_tree_t *tree)
{
        driver_t *drv;

        assert(dev != NULL);
        assert(drivers_list != NULL);
        assert(tree != NULL);

        /*
         * Find the next best driver for this device.
         */
again:
        drv = find_best_match_driver(drivers_list, dev);
        if (drv == NULL) {
                log_msg(LOG_DEFAULT, LVL_ERROR, "No driver found for device `%s'.",
                    dev->pfun->pathname);
                return false;
        }

        /* Attach the driver to the device. */
        attach_driver(tree, dev, drv);

        fibril_mutex_lock(&drv->driver_mutex);
        if (drv->state == DRIVER_NOT_STARTED) {
                /* Start the driver. */
                start_driver(drv);
        }
        bool is_running = drv->state == DRIVER_RUNNING;
        fibril_mutex_unlock(&drv->driver_mutex);

        /* Notify the driver about the new device. */
        if (is_running) {
                add_device(drv, dev, tree);

                /* If the device probe failed, need to try next available driver */
                if (dev->state == DEVICE_NOT_PRESENT)
                        goto again;
        }

        fibril_mutex_lock(&drv->driver_mutex);
        fibril_mutex_unlock(&drv->driver_mutex);

        fibril_rwlock_write_lock(&tree->rwlock);
        if (dev->pfun != NULL) {
                dev->pfun->state = FUN_ON_LINE;
        }
        fibril_rwlock_write_unlock(&tree->rwlock);
        return true;
}

/** Pass a device to running driver.
 *
 * @param drv           The driver's structure.
 * @param dev           The device's node in the device tree.
 */
void add_device(driver_t *drv, dev_node_t *dev, dev_tree_t *tree)
{
        /*
         * We do not expect to have driver's mutex locked as we do not
         * access any structures that would affect driver_t.
         */
        log_msg(LOG_DEFAULT, LVL_DEBUG, "add_device(drv=\"%s\", dev=\"%s\")",
            drv->name, dev->pfun->name);

        /* Send the device to the driver. */
        devman_handle_t parent_handle;
        if (dev->pfun) {
                parent_handle = dev->pfun->handle;
        } else {
                parent_handle = 0;
        }

        async_exch_t *exch = async_exchange_begin(drv->sess);

        ipc_call_t answer;
        aid_t req = async_send_2(exch, DRIVER_DEV_ADD, dev->handle,
            parent_handle, &answer);

        /* Send the device name to the driver. */
        errno_t rc = async_data_write_start(exch, dev->pfun->name,
            str_size(dev->pfun->name) + 1);

        async_exchange_end(exch);

        if (rc != EOK) {
                async_forget(req);
        } else {
                /* Wait for answer from the driver. */
                async_wait_for(req, &rc);
        }

        switch (rc) {
        case EOK:
                dev->state = DEVICE_USABLE;
                break;
        case ENOENT:
                dev->state = DEVICE_NOT_PRESENT;
                break;
        default:
                dev->state = DEVICE_INVALID;
                break;
        }

        dev->passed_to_driver = true;
}

errno_t driver_dev_remove(dev_tree_t *tree, dev_node_t *dev)
{
        async_exch_t *exch;
        errno_t retval;
        driver_t *drv;
        devman_handle_t handle;

        assert(dev != NULL);

        log_msg(LOG_DEFAULT, LVL_DEBUG, "driver_dev_remove(%p)", dev);

        fibril_rwlock_read_lock(&tree->rwlock);
        drv = dev->drv;
        handle = dev->handle;
        fibril_rwlock_read_unlock(&tree->rwlock);

        exch = async_exchange_begin(drv->sess);
        retval = async_req_1_0(exch, DRIVER_DEV_REMOVE, handle);
        async_exchange_end(exch);

        return retval;
}

errno_t driver_dev_gone(dev_tree_t *tree, dev_node_t *dev)
{
        async_exch_t *exch;
        errno_t retval;
        driver_t *drv;
        devman_handle_t handle;

        assert(dev != NULL);

        log_msg(LOG_DEFAULT, LVL_DEBUG, "driver_dev_gone(%p)", dev);

        fibril_rwlock_read_lock(&tree->rwlock);
        drv = dev->drv;
        handle = dev->handle;
        fibril_rwlock_read_unlock(&tree->rwlock);

        exch = async_exchange_begin(drv->sess);
        retval = async_req_1_0(exch, DRIVER_DEV_GONE, handle);
        async_exchange_end(exch);

        return retval;
}

errno_t driver_fun_online(dev_tree_t *tree, fun_node_t *fun)
{
        async_exch_t *exch;
        errno_t retval;
        driver_t *drv;
        devman_handle_t handle;

        log_msg(LOG_DEFAULT, LVL_DEBUG, "driver_fun_online(%p)", fun);

        fibril_rwlock_read_lock(&tree->rwlock);

        if (fun->dev == NULL) {
                /* XXX root function? */
                fibril_rwlock_read_unlock(&tree->rwlock);
                return EINVAL;
        }

        drv = fun->dev->drv;
        handle = fun->handle;
        fibril_rwlock_read_unlock(&tree->rwlock);

        exch = async_exchange_begin(drv->sess);
        retval = async_req_1_0(exch, DRIVER_FUN_ONLINE, handle);
        loc_exchange_end(exch);

        return retval;
}

errno_t driver_fun_offline(dev_tree_t *tree, fun_node_t *fun)
{
        async_exch_t *exch;
        errno_t retval;
        driver_t *drv;
        devman_handle_t handle;

        log_msg(LOG_DEFAULT, LVL_DEBUG, "driver_fun_offline(%p)", fun);

        fibril_rwlock_read_lock(&tree->rwlock);
        if (fun->dev == NULL) {
                /* XXX root function? */
                fibril_rwlock_read_unlock(&tree->rwlock);
                return EINVAL;
        }

        drv = fun->dev->drv;
        handle = fun->handle;
        fibril_rwlock_read_unlock(&tree->rwlock);

        exch = async_exchange_begin(drv->sess);
        retval = async_req_1_0(exch, DRIVER_FUN_OFFLINE, handle);
        loc_exchange_end(exch);

        return retval;

}

/** Get list of registered drivers. */
errno_t driver_get_list(driver_list_t *driver_list, devman_handle_t *hdl_buf,
    size_t buf_size, size_t *act_size)
{
        size_t act_cnt;
        size_t buf_cnt;

        fibril_mutex_lock(&driver_list->drivers_mutex);

        buf_cnt = buf_size / sizeof(devman_handle_t);

        act_cnt = list_count(&driver_list->drivers);
        *act_size = act_cnt * sizeof(devman_handle_t);

        if (buf_size % sizeof(devman_handle_t) != 0) {
                fibril_mutex_unlock(&driver_list->drivers_mutex);
                return EINVAL;
        }

        size_t pos = 0;
        list_foreach(driver_list->drivers, drivers, driver_t, drv) {
                if (pos < buf_cnt) {
                        hdl_buf[pos] = drv->handle;
                }

                pos++;
        }

        fibril_mutex_unlock(&driver_list->drivers_mutex);
        return EOK;
}

/** Get list of device functions. */
errno_t driver_get_devices(driver_t *driver, devman_handle_t *hdl_buf,
    size_t buf_size, size_t *act_size)
{
        size_t act_cnt;
        size_t buf_cnt;

        fibril_mutex_lock(&driver->driver_mutex);

        buf_cnt = buf_size / sizeof(devman_handle_t);

        act_cnt = list_count(&driver->devices);
        *act_size = act_cnt * sizeof(devman_handle_t);

        if (buf_size % sizeof(devman_handle_t) != 0) {
                fibril_mutex_unlock(&driver->driver_mutex);
                return EINVAL;
        }

        size_t pos = 0;
        list_foreach(driver->devices, driver_devices, dev_node_t, dev) {
                if (pos < buf_cnt) {
                        hdl_buf[pos] = dev->handle;
                }

                pos++;
        }

        fibril_mutex_unlock(&driver->driver_mutex);
        return EOK;
}

/** Try to find next available driver in a separate fibril.
 *
 * @param arg Device node (dev_node_t)
 */
static errno_t driver_reassign_fibril(void *arg)
{
        dev_node_t *dev_node = (dev_node_t *) arg;
        assign_driver(dev_node, &drivers_list, &device_tree);

        /* Delete one reference we got from the caller. */
        dev_del_ref(dev_node);
        return EOK;
}

/** @}
 */