bus_for_each_dev - while 조건문

/**
 * bus_for_each_dev - device iterator.
 * @bus: bus type.
 * @start: device to start iterating from.
 * @data: data for the callback.
 * @fn: function to be called for each device.
 *
 * Iterate over @bus's list of devices, and call @fn for each,
 * passing it @data. If @start is not NULL, we use that device to
 * begin iterating from.
 *
 * We check the return of @fn each time. If it returns anything
 * other than 0, we break out and return that value.
 *
 * NOTE: The device that returns a non-zero value is not retained
 * in any way, nor is its refcount incremented. If the caller needs
 * to retain this data, it should do so, and increment the reference
 * count in the supplied callback.
 */
linux/drivers/base/bus.c
int bus_for_each_dev(struct bus_type *bus, struct device *start,
                     void *data, int (*fn)(struct device *, void *))
{
        struct klist_iter i;
        struct device *dev;
        int error = 0; 

        if (!bus || !bus->p)
                return -EINVAL;

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

while문을 보시라
이렇게 이쁘게도 할 수 있구나