linux/drivers/base/bus.c

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/*
* bus.c - bus 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/device.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/string.h>
#include "base.h"
#include "power/power.h"
#define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
#define to_bus(obj) container_of(obj, struct bus_type, subsys.kset.kobj)
/*
* sysfs bindings for drivers
*/
#define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)
#define to_driver(obj) container_of(obj, struct device_driver, kobj)
static ssize_t
drv_attr_show(struct kobject * kobj, struct attribute * attr, char * buf)
{
struct driver_attribute * drv_attr = to_drv_attr(attr);
struct device_driver * drv = to_driver(kobj);
ssize_t ret = -EIO;
if (drv_attr->show)
ret = drv_attr->show(drv, buf);
return ret;
}
static ssize_t
drv_attr_store(struct kobject * kobj, struct attribute * attr,
const char * buf, size_t count)
{
struct driver_attribute * drv_attr = to_drv_attr(attr);
struct device_driver * drv = to_driver(kobj);
ssize_t ret = -EIO;
if (drv_attr->store)
ret = drv_attr->store(drv, buf, count);
return ret;
}
static struct sysfs_ops driver_sysfs_ops = {
.show = drv_attr_show,
.store = drv_attr_store,
};
static void driver_release(struct kobject * kobj)
{
struct device_driver * drv = to_driver(kobj);
complete(&drv->unloaded);
}
static struct kobj_type ktype_driver = {
.sysfs_ops = &driver_sysfs_ops,
.release = driver_release,
};
/*
* sysfs bindings for buses
*/
static ssize_t
bus_attr_show(struct kobject * kobj, struct attribute * attr, char * buf)
{
struct bus_attribute * bus_attr = to_bus_attr(attr);
struct bus_type * bus = to_bus(kobj);
ssize_t ret = 0;
if (bus_attr->show)
ret = bus_attr->show(bus, buf);
return ret;
}
static ssize_t
bus_attr_store(struct kobject * kobj, struct attribute * attr,
const char * buf, size_t count)
{
struct bus_attribute * bus_attr = to_bus_attr(attr);
struct bus_type * bus = to_bus(kobj);
ssize_t ret = 0;
if (bus_attr->store)
ret = bus_attr->store(bus, buf, count);
return ret;
}
static struct sysfs_ops bus_sysfs_ops = {
.show = bus_attr_show,
.store = bus_attr_store,
};
int bus_create_file(struct bus_type * bus, struct bus_attribute * attr)
{
int error;
if (get_bus(bus)) {
error = sysfs_create_file(&bus->subsys.kset.kobj, &attr->attr);
put_bus(bus);
} else
error = -EINVAL;
return error;
}
void bus_remove_file(struct bus_type * bus, struct bus_attribute * attr)
{
if (get_bus(bus)) {
sysfs_remove_file(&bus->subsys.kset.kobj, &attr->attr);
put_bus(bus);
}
}
static struct kobj_type ktype_bus = {
.sysfs_ops = &bus_sysfs_ops,
};
static decl_subsys(bus, &ktype_bus, NULL);
#ifdef CONFIG_HOTPLUG
/* Manually detach a device from its associated driver. */
static int driver_helper(struct device *dev, void *data)
{
const char *name = data;
if (strcmp(name, dev->bus_id) == 0)
return 1;
return 0;
}
static ssize_t driver_unbind(struct device_driver *drv,
const char *buf, size_t count)
{
struct bus_type *bus = get_bus(drv->bus);
struct device *dev;
int err = -ENODEV;
dev = bus_find_device(bus, NULL, (void *)buf, driver_helper);
if (dev && dev->driver == drv) {
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
device_release_driver(dev);
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
if (dev->parent)
up(&dev->parent->sem);
err = count;
}
put_device(dev);
put_bus(bus);
return err;
}
static DRIVER_ATTR(unbind, S_IWUSR, NULL, driver_unbind);
/*
* Manually attach a device to a driver.
* Note: the driver must want to bind to the device,
* it is not possible to override the driver's id table.
*/
static ssize_t driver_bind(struct device_driver *drv,
const char *buf, size_t count)
{
struct bus_type *bus = get_bus(drv->bus);
struct device *dev;
int err = -ENODEV;
dev = bus_find_device(bus, NULL, (void *)buf, driver_helper);
if (dev && dev->driver == NULL) {
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
down(&dev->sem);
err = driver_probe_device(drv, dev);
up(&dev->sem);
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
if (dev->parent)
up(&dev->parent->sem);
if (err > 0) /* success */
err = count;
else if (err == 0) /* driver didn't accept device */
err = -ENODEV;
}
put_device(dev);
put_bus(bus);
return err;
}
static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind);
#endif
static struct device * next_device(struct klist_iter * i)
{
struct klist_node * n = klist_next(i);
return n ? container_of(n, struct device, knode_bus) : NULL;
}
/**
* 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, and increment the reference
* count in the supplied callback.
*/
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)
return -EINVAL;
klist_iter_init_node(&bus->klist_devices, &i,
(start ? &start->knode_bus : NULL));
while ((dev = next_device(&i)) && !error)
error = fn(dev, data);
klist_iter_exit(&i);
return error;
}
/**
* bus_find_device - device iterator for locating a particular device.
* @bus: bus type
* @start: Device to begin with
* @data: Data to pass to match function
* @match: Callback function to check device
*
* This is similar to the bus_for_each_dev() 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 * bus_find_device(struct bus_type *bus,
struct device *start, void *data,
int (*match)(struct device *, void *))
{
struct klist_iter i;
struct device *dev;
if (!bus)
return NULL;
klist_iter_init_node(&bus->klist_devices, &i,
(start ? &start->knode_bus : NULL));
while ((dev = next_device(&i)))
if (match(dev, data) && get_device(dev))
break;
klist_iter_exit(&i);
return dev;
}
static struct device_driver * next_driver(struct klist_iter * i)
{
struct klist_node * n = klist_next(i);
return n ? container_of(n, struct device_driver, knode_bus) : NULL;
}
/**
* bus_for_each_drv - driver iterator
* @bus: bus we're dealing with.
* @start: driver to start iterating on.
* @data: data to pass to the callback.
* @fn: function to call for each driver.
*
* This is nearly identical to the device iterator above.
* We iterate over each driver that belongs to @bus, and call
* @fn for each. If @fn returns anything but 0, we break out
* and return it. If @start is not NULL, we use it as the head
* of the list.
*
* NOTE: we don't return the driver that returns a non-zero
* value, nor do we leave the reference count incremented for that
* driver. If the caller needs to know that info, it must set it
* in the callback. It must also be sure to increment the refcount
* so it doesn't disappear before returning to the caller.
*/
int bus_for_each_drv(struct bus_type * bus, struct device_driver * start,
void * data, int (*fn)(struct device_driver *, void *))
{
struct klist_iter i;
struct device_driver * drv;
int error = 0;
if (!bus)
return -EINVAL;
klist_iter_init_node(&bus->klist_drivers, &i,
start ? &start->knode_bus : NULL);
while ((drv = next_driver(&i)) && !error)
error = fn(drv, data);
klist_iter_exit(&i);
return error;
}
static int device_add_attrs(struct bus_type * bus, struct device * dev)
{
int error = 0;
int i;
if (bus->dev_attrs) {
for (i = 0; attr_name(bus->dev_attrs[i]); i++) {
error = device_create_file(dev,&bus->dev_attrs[i]);
if (error)
goto Err;
}
}
Done:
return error;
Err:
while (--i >= 0)
device_remove_file(dev,&bus->dev_attrs[i]);
goto Done;
}
static void device_remove_attrs(struct bus_type * bus, struct device * dev)
{
int i;
if (bus->dev_attrs) {
for (i = 0; attr_name(bus->dev_attrs[i]); i++)
device_remove_file(dev,&bus->dev_attrs[i]);
}
}
#ifdef CONFIG_SYSFS_DEPRECATED
static int make_deprecated_bus_links(struct device *dev)
{
return sysfs_create_link(&dev->kobj,
&dev->bus->subsys.kset.kobj, "bus");
}
static void remove_deprecated_bus_links(struct device *dev)
{
sysfs_remove_link(&dev->kobj, "bus");
}
#else
static inline int make_deprecated_bus_links(struct device *dev) { return 0; }
static inline void remove_deprecated_bus_links(struct device *dev) { }
#endif
/**
* bus_add_device - add device to bus
* @dev: device being added
*
* - Add the device to its bus's list of devices.
* - Create link to device's bus.
*/
int bus_add_device(struct device * dev)
{
struct bus_type * bus = get_bus(dev->bus);
int error = 0;
if (bus) {
pr_debug("bus %s: add device %s\n", bus->name, dev->bus_id);
error = device_add_attrs(bus, dev);
if (error)
goto out_put;
error = sysfs_create_link(&bus->devices.kobj,
&dev->kobj, dev->bus_id);
if (error)
goto out_id;
error = sysfs_create_link(&dev->kobj,
&dev->bus->subsys.kset.kobj, "subsystem");
if (error)
goto out_subsys;
error = make_deprecated_bus_links(dev);
if (error)
goto out_deprecated;
}
return 0;
out_deprecated:
sysfs_remove_link(&dev->kobj, "subsystem");
out_subsys:
sysfs_remove_link(&bus->devices.kobj, dev->bus_id);
out_id:
device_remove_attrs(bus, dev);
out_put:
put_bus(dev->bus);
return error;
}
/**
* bus_attach_device - add device to bus
* @dev: device tried to attach to a driver
*
2006-09-18 20:22:34 +00:00
* - Add device to bus's list of devices.
* - Try to attach to driver.
*/
int bus_attach_device(struct device * dev)
{
struct bus_type *bus = dev->bus;
int ret = 0;
if (bus) {
2006-09-18 20:22:34 +00:00
dev->is_registered = 1;
ret = device_attach(dev);
if (ret >= 0) {
klist_add_tail(&dev->knode_bus, &bus->klist_devices);
ret = 0;
2006-09-18 20:22:34 +00:00
} else
dev->is_registered = 0;
}
return ret;
}
/**
* bus_remove_device - remove device from bus
* @dev: device to be removed
*
* - Remove symlink from bus's directory.
* - Delete device from bus's list.
* - Detach from its driver.
* - Drop reference taken in bus_add_device().
*/
void bus_remove_device(struct device * dev)
{
if (dev->bus) {
sysfs_remove_link(&dev->kobj, "subsystem");
remove_deprecated_bus_links(dev);
sysfs_remove_link(&dev->bus->devices.kobj, dev->bus_id);
device_remove_attrs(dev->bus, dev);
if (dev->is_registered) {
dev->is_registered = 0;
klist_del(&dev->knode_bus);
}
pr_debug("bus %s: remove device %s\n", dev->bus->name, dev->bus_id);
device_release_driver(dev);
put_bus(dev->bus);
}
}
static int driver_add_attrs(struct bus_type * bus, struct device_driver * drv)
{
int error = 0;
int i;
if (bus->drv_attrs) {
for (i = 0; attr_name(bus->drv_attrs[i]); i++) {
error = driver_create_file(drv, &bus->drv_attrs[i]);
if (error)
goto Err;
}
}
Done:
return error;
Err:
while (--i >= 0)
driver_remove_file(drv, &bus->drv_attrs[i]);
goto Done;
}
static void driver_remove_attrs(struct bus_type * bus, struct device_driver * drv)
{
int i;
if (bus->drv_attrs) {
for (i = 0; attr_name(bus->drv_attrs[i]); i++)
driver_remove_file(drv, &bus->drv_attrs[i]);
}
}
#ifdef CONFIG_HOTPLUG
/*
* Thanks to drivers making their tables __devinit, we can't allow manual
* bind and unbind from userspace unless CONFIG_HOTPLUG is enabled.
*/
static int __must_check add_bind_files(struct device_driver *drv)
{
int ret;
ret = driver_create_file(drv, &driver_attr_unbind);
if (ret == 0) {
ret = driver_create_file(drv, &driver_attr_bind);
if (ret)
driver_remove_file(drv, &driver_attr_unbind);
}
return ret;
}
static void remove_bind_files(struct device_driver *drv)
{
driver_remove_file(drv, &driver_attr_bind);
driver_remove_file(drv, &driver_attr_unbind);
}
#else
static inline int add_bind_files(struct device_driver *drv) { return 0; }
static inline void remove_bind_files(struct device_driver *drv) {}
#endif
/**
* bus_add_driver - Add a driver to the bus.
* @drv: driver.
*
*/
int bus_add_driver(struct device_driver *drv)
{
struct bus_type * bus = get_bus(drv->bus);
int error = 0;
if (!bus)
return 0;
pr_debug("bus %s: add driver %s\n", bus->name, drv->name);
error = kobject_set_name(&drv->kobj, "%s", drv->name);
if (error)
goto out_put_bus;
drv->kobj.kset = &bus->drivers;
if ((error = kobject_register(&drv->kobj)))
goto out_put_bus;
error = driver_attach(drv);
if (error)
goto out_unregister;
klist_add_tail(&drv->knode_bus, &bus->klist_drivers);
module_add_driver(drv->owner, drv);
error = driver_add_attrs(bus, drv);
if (error) {
/* How the hell do we get out of this pickle? Give up */
printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",
__FUNCTION__, drv->name);
}
error = add_bind_files(drv);
if (error) {
/* Ditto */
printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
__FUNCTION__, drv->name);
}
return error;
out_unregister:
kobject_unregister(&drv->kobj);
out_put_bus:
put_bus(bus);
return error;
}
/**
* bus_remove_driver - delete driver from bus's knowledge.
* @drv: driver.
*
* Detach the driver from the devices it controls, and remove
* it from its bus's list of drivers. Finally, we drop the reference
* to the bus we took in bus_add_driver().
*/
void bus_remove_driver(struct device_driver * drv)
{
if (!drv->bus)
return;
remove_bind_files(drv);
driver_remove_attrs(drv->bus, drv);
klist_remove(&drv->knode_bus);
pr_debug("bus %s: remove driver %s\n", drv->bus->name, drv->name);
driver_detach(drv);
module_remove_driver(drv);
kobject_unregister(&drv->kobj);
put_bus(drv->bus);
}
/* Helper for bus_rescan_devices's iter */
static int __must_check bus_rescan_devices_helper(struct device *dev,
void *data)
{
int ret = 0;
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
if (!dev->driver) {
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
ret = device_attach(dev);
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
if (dev->parent)
up(&dev->parent->sem);
if (ret > 0)
ret = 0;
[PATCH] Hold the device's parent's lock during probe and remove This patch (as604) makes the driver core hold a device's parent's lock as well as the device's lock during calls to the probe and remove methods in a driver. This facility is needed by USB device drivers, owing to the peculiar way USB devices work: A device provides multiple interfaces, and drivers are bound to interfaces rather than to devices; Nevertheless a reset, reset-configuration, suspend, or resume affects the entire device and requires the caller to hold the lock for the device, not just a lock for one of the interfaces. Since a USB driver's probe method is always called with the interface lock held, the locking order rules (always lock parent before child) prevent these methods from acquiring the device lock. The solution provided here is to call all probe and remove methods, for all devices (not just USB), with the parent lock already acquired. Although currently only the USB subsystem requires these changes, people have mentioned in prior discussion that the overhead of acquiring an extra semaphore in all the prove/remove sequences is not overly large. Up to now, the USB core has been using its own set of private semaphores. A followup patch will remove them, relying entirely on the device semaphores provided by the driver core. The code paths affected by this patch are: device_add and device_del: The USB core already holds the parent lock, so no actual change is needed. driver_register and driver_unregister: The driver core will now lock both the parent and the device before probing or removing. driver_bind and driver_unbind (in sysfs): These routines will now lock both the parent and the device before binding or unbinding. bus_rescan_devices: The helper routine will lock the parent before probing a device. I have not tested this patch for conflicts with other subsystems. As far as I can see, the only possibility of conflict would lie in the bus_rescan_devices pathway, and it seems pretty remote. Nevertheless, it would be good for this to get a lot of testing in -mm. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2005-11-17 21:54:12 +00:00
}
return ret < 0 ? ret : 0;
}
/**
* bus_rescan_devices - rescan devices on the bus for possible drivers
* @bus: the bus to scan.
*
* This function will look for devices on the bus with no driver
* attached and rescan it against existing drivers to see if it matches
* any by calling device_attach() for the unbound devices.
*/
int bus_rescan_devices(struct bus_type * bus)
{
return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
}
/**
* device_reprobe - remove driver for a device and probe for a new driver
* @dev: the device to reprobe
*
* This function detaches the attached driver (if any) for the given
* device and restarts the driver probing process. It is intended
* to use if probing criteria changed during a devices lifetime and
* driver attachment should change accordingly.
*/
int device_reprobe(struct device *dev)
{
if (dev->driver) {
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
device_release_driver(dev);
if (dev->parent)
up(&dev->parent->sem);
}
return bus_rescan_devices_helper(dev, NULL);
}
EXPORT_SYMBOL_GPL(device_reprobe);
struct bus_type *get_bus(struct bus_type *bus)
{
return bus ? container_of(subsys_get(&bus->subsys),
struct bus_type, subsys) : NULL;
}
void put_bus(struct bus_type * bus)
{
subsys_put(&bus->subsys);
}
/**
* find_bus - locate bus by name.
* @name: name of bus.
*
* Call kset_find_obj() to iterate over list of buses to
* find a bus by name. Return bus if found.
*
* Note that kset_find_obj increments bus' reference count.
*/
#if 0
struct bus_type * find_bus(char * name)
{
struct kobject * k = kset_find_obj(&bus_subsys.kset, name);
return k ? to_bus(k) : NULL;
}
#endif /* 0 */
/**
* bus_add_attrs - Add default attributes for this bus.
* @bus: Bus that has just been registered.
*/
static int bus_add_attrs(struct bus_type * bus)
{
int error = 0;
int i;
if (bus->bus_attrs) {
for (i = 0; attr_name(bus->bus_attrs[i]); i++) {
if ((error = bus_create_file(bus,&bus->bus_attrs[i])))
goto Err;
}
}
Done:
return error;
Err:
while (--i >= 0)
bus_remove_file(bus,&bus->bus_attrs[i]);
goto Done;
}
static void bus_remove_attrs(struct bus_type * bus)
{
int i;
if (bus->bus_attrs) {
for (i = 0; attr_name(bus->bus_attrs[i]); i++)
bus_remove_file(bus,&bus->bus_attrs[i]);
}
}
static void klist_devices_get(struct klist_node *n)
{
struct device *dev = container_of(n, struct device, knode_bus);
get_device(dev);
}
static void klist_devices_put(struct klist_node *n)
{
struct device *dev = container_of(n, struct device, knode_bus);
put_device(dev);
}
/**
* bus_register - register a bus with the system.
* @bus: bus.
*
* Once we have that, we registered the bus with the kobject
* infrastructure, then register the children subsystems it has:
* the devices and drivers that belong to the bus.
*/
int bus_register(struct bus_type * bus)
{
int retval;
Driver core: add notification of bus events I finally did as you suggested and added the notifier to the struct bus_type itself. There are still problems to be expected is something attaches to a bus type where the code can hook in different struct device sub-classes (which is imho a big bogosity but I won't even try to argue that case now) but it will solve nicely a number of issues I've had so far. That also means that clients interested in registering for such notifications have to do it before devices are added and after bus types are registered. Fortunately, most bus types that matter for the various usage scenarios I have in mind are registerd at postcore_initcall time, which means I have a really nice spot at arch_initcall time to add my notifiers. There are 4 notifications provided. Device being added (before hooked to the bus) and removed (failure of previous case or after being unhooked from the bus), along with driver being bound to a device and about to be unbound. The usage I have for these are: - The 2 first ones are used to maintain a struct device_ext that is hooked to struct device.firmware_data. This structure contains for now a pointer to the Open Firmware node related to the device (if any), the NUMA node ID (for quick access to it) and the DMA operations pointers & iommu table instance for DMA to/from this device. For bus types I own (like IBM VIO or EBUS), I just maintain that structure directly from the bus code when creating the devices. But for bus types managed by generic code like PCI or platform (actually, of_platform which is a variation of platform linked to Open Firmware device-tree), I need this notifier. - The other two ones have a completely different usage scenario. I have cases where multiple devices and their drivers depend on each other. For example, the IBM EMAC network driver needs to attach to a MAL DMA engine which is a separate device, and a PHY interface which is also a separate device. They are all of_platform_device's (well, about to be with my upcoming patches) but there is no say in what precise order the core will "probe" them and instanciate the various modules. The solution I found for that is to have the drivers for emac to use multithread_probe, and wait for a driver to be bound to the target MAL and PHY control devices (the device-tree contains reference to the MAL and PHY interface nodes, which I can then match to of_platform_devices). Right now, I've been polling, but with that notifier, I can more cleanly wait (with a timeout of course). Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-10-25 03:44:59 +00:00
BLOCKING_INIT_NOTIFIER_HEAD(&bus->bus_notifier);
retval = kobject_set_name(&bus->subsys.kset.kobj, "%s", bus->name);
if (retval)
goto out;
subsys_set_kset(bus, bus_subsys);
retval = subsystem_register(&bus->subsys);
if (retval)
goto out;
kobject_set_name(&bus->devices.kobj, "devices");
bus->devices.subsys = &bus->subsys;
retval = kset_register(&bus->devices);
if (retval)
goto bus_devices_fail;
kobject_set_name(&bus->drivers.kobj, "drivers");
bus->drivers.subsys = &bus->subsys;
bus->drivers.ktype = &ktype_driver;
retval = kset_register(&bus->drivers);
if (retval)
goto bus_drivers_fail;
klist_init(&bus->klist_devices, klist_devices_get, klist_devices_put);
klist_init(&bus->klist_drivers, NULL, NULL);
retval = bus_add_attrs(bus);
if (retval)
goto bus_attrs_fail;
pr_debug("bus type '%s' registered\n", bus->name);
return 0;
bus_attrs_fail:
kset_unregister(&bus->drivers);
bus_drivers_fail:
kset_unregister(&bus->devices);
bus_devices_fail:
subsystem_unregister(&bus->subsys);
out:
return retval;
}
/**
* bus_unregister - remove a bus from the system
* @bus: bus.
*
* Unregister the child subsystems and the bus itself.
* Finally, we call put_bus() to release the refcount
*/
void bus_unregister(struct bus_type * bus)
{
pr_debug("bus %s: unregistering\n", bus->name);
bus_remove_attrs(bus);
kset_unregister(&bus->drivers);
kset_unregister(&bus->devices);
subsystem_unregister(&bus->subsys);
}
Driver core: add notification of bus events I finally did as you suggested and added the notifier to the struct bus_type itself. There are still problems to be expected is something attaches to a bus type where the code can hook in different struct device sub-classes (which is imho a big bogosity but I won't even try to argue that case now) but it will solve nicely a number of issues I've had so far. That also means that clients interested in registering for such notifications have to do it before devices are added and after bus types are registered. Fortunately, most bus types that matter for the various usage scenarios I have in mind are registerd at postcore_initcall time, which means I have a really nice spot at arch_initcall time to add my notifiers. There are 4 notifications provided. Device being added (before hooked to the bus) and removed (failure of previous case or after being unhooked from the bus), along with driver being bound to a device and about to be unbound. The usage I have for these are: - The 2 first ones are used to maintain a struct device_ext that is hooked to struct device.firmware_data. This structure contains for now a pointer to the Open Firmware node related to the device (if any), the NUMA node ID (for quick access to it) and the DMA operations pointers & iommu table instance for DMA to/from this device. For bus types I own (like IBM VIO or EBUS), I just maintain that structure directly from the bus code when creating the devices. But for bus types managed by generic code like PCI or platform (actually, of_platform which is a variation of platform linked to Open Firmware device-tree), I need this notifier. - The other two ones have a completely different usage scenario. I have cases where multiple devices and their drivers depend on each other. For example, the IBM EMAC network driver needs to attach to a MAL DMA engine which is a separate device, and a PHY interface which is also a separate device. They are all of_platform_device's (well, about to be with my upcoming patches) but there is no say in what precise order the core will "probe" them and instanciate the various modules. The solution I found for that is to have the drivers for emac to use multithread_probe, and wait for a driver to be bound to the target MAL and PHY control devices (the device-tree contains reference to the MAL and PHY interface nodes, which I can then match to of_platform_devices). Right now, I've been polling, but with that notifier, I can more cleanly wait (with a timeout of course). Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-10-25 03:44:59 +00:00
int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
{
return blocking_notifier_chain_register(&bus->bus_notifier, nb);
}
EXPORT_SYMBOL_GPL(bus_register_notifier);
int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
{
return blocking_notifier_chain_unregister(&bus->bus_notifier, nb);
}
EXPORT_SYMBOL_GPL(bus_unregister_notifier);
int __init buses_init(void)
{
return subsystem_register(&bus_subsys);
}
EXPORT_SYMBOL_GPL(bus_for_each_dev);
EXPORT_SYMBOL_GPL(bus_find_device);
EXPORT_SYMBOL_GPL(bus_for_each_drv);
EXPORT_SYMBOL_GPL(bus_register);
EXPORT_SYMBOL_GPL(bus_unregister);
EXPORT_SYMBOL_GPL(bus_rescan_devices);
EXPORT_SYMBOL_GPL(bus_create_file);
EXPORT_SYMBOL_GPL(bus_remove_file);