driver.c

/*
 * driver.c - centralized device driver management
 *
 * Copyright (c) 2002-3 Patrick Mochel
 * Copyright (c) 2002-3 Open Source Development Labs
 *
 * This file is released under the GPLv2
 *
 */

#include <linux/config.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/string.h>
#include "base.h"

#define to_dev(node) container_of(node, struct device, driver_list)
#define to_drv(obj) container_of(obj, struct device_driver, kobj)


/**
 *	driver_for_each_device - Iterator for devices bound to a driver.
 *	@drv:	Driver we're iterating.
 *	@data:	Data to pass to the callback.
 *	@fn:	Function to call for each device.
 *
 *	Take the bus's rwsem and 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, int (*fn)(struct device *, void *))
{
	struct list_head * head;
	struct device * dev;
	int error = 0;

	down_read(&drv->bus->subsys.rwsem);
	head = &drv->devices;
	dev = list_prepare_entry(start, head, driver_list);
	list_for_each_entry_continue(dev, head, driver_list) {
		get_device(dev);
		error = fn(dev, data);
		put_device(dev);
		if (error)
			break;
	}
	up_read(&drv->bus->subsys.rwsem);
	return error;
}

EXPORT_SYMBOL(driver_for_each_device);


/**
 *	driver_create_file - create sysfs file for driver.
 *	@drv:	driver.
 *	@attr:	driver attribute descriptor.
 */

int driver_create_file(struct device_driver * drv, struct driver_attribute * attr)
{
	int error;
	if (get_driver(drv)) {
		error = sysfs_create_file(&drv->kobj, &attr->attr);
		put_driver(drv);
	} else
		error = -EINVAL;
	return error;
}


/**
 *	driver_remove_file - remove sysfs file for driver.
 *	@drv:	driver.
 *	@attr:	driver attribute descriptor.
 */

void driver_remove_file(struct device_driver * drv, struct driver_attribute * attr)
{
	if (get_driver(drv)) {
		sysfs_remove_file(&drv->kobj, &attr->attr);
		put_driver(drv);
	}
}


/**
 *	get_driver - increment driver reference count.
 *	@drv:	driver.
 */
struct device_driver * get_driver(struct device_driver * drv)
{
	return drv ? to_drv(kobject_get(&drv->kobj)) : NULL;
}


/**
 *	put_driver - decrement driver's refcount.
 *	@drv:	driver.
 */
void put_driver(struct device_driver * drv)
{
	kobject_put(&drv->kobj);
}


/**
 *	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.
 *
 *	The one interesting aspect is that we setup @drv->unloaded
 *	as a completion that gets complete when the driver reference
 *	count reaches 0.
 */
int driver_register(struct device_driver * drv)
{
	INIT_LIST_HEAD(&drv->devices);
	init_completion(&drv->unloaded);
	return bus_add_driver(drv);
}


/**
 *	driver_unregister - remove driver from system.
 *	@drv:	driver.
 *
 *	Again, we pass off most of the work to the bus-level call.
 *
 *	Though, once that is done, we wait until @drv->unloaded is completed.
 *	This will block until the driver refcount reaches 0, and it is
 *	released. Only modular drivers will call this function, and we
 *	have to guarantee that it won't complete, letting the driver
 *	unload until all references are gone.
 */

void driver_unregister(struct device_driver * drv)
{
	bus_remove_driver(drv);
	wait_for_completion(&drv->unloaded);
}

/**
 *	driver_find - locate driver on a bus by its name.
 *	@name:	name of the driver.
 *	@bus:	bus to scan for the driver.
 *
 *	Call kset_find_obj() to iterate over list of drivers on
 *	a bus to find driver by name. Return driver if found.
 *
 *	Note that kset_find_obj increments driver's reference count.
 */
struct device_driver *driver_find(const char *name, struct bus_type *bus)
{
	struct kobject *k = kset_find_obj(&bus->drivers, name);
	if (k)
		return to_drv(k);
	return NULL;
}

EXPORT_SYMBOL_GPL(driver_register);
EXPORT_SYMBOL_GPL(driver_unregister);
EXPORT_SYMBOL_GPL(get_driver);
EXPORT_SYMBOL_GPL(put_driver);
EXPORT_SYMBOL_GPL(driver_find);

EXPORT_SYMBOL_GPL(driver_create_file);
EXPORT_SYMBOL_GPL(driver_remove_file);