/**
* 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)
{
if ((drv->bus->probe && drv->probe) ||
(drv->bus->remove && drv->remove) ||
(drv->bus->shutdown && drv->shutdown)) {
printk(KERN_WARNING "Driver '%s' needs updating - please use bus_type methods\n", drv->name);
}
klist_init(&drv->klist_devices, NULL, NULL);
init_completion(&drv->unloaded);
return bus_add_driver(drv);
}
1.4 bus_add_driver()函數(shù)
在文件drivers/base/bus.c中實(shí)現(xiàn)了bus_add_driver()函數(shù)，它通過(guò)語(yǔ)句klist_add_tail(&drv->knode_bus, &bus->klist_drivers); 將驅(qū)動(dòng)信息保存到總線結(jié)構(gòu)中，在設(shè)備注冊(cè)過(guò)程中，我們就可以明白此語(yǔ)句的作用了。在此語(yǔ)句之前，調(diào)用了driver_attach()函數(shù)。
/**
* 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;
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);
}
1.5 dd.c文件
在文件drivers/base/dd.c中，實(shí)現(xiàn)了設(shè)備與驅(qū)動(dòng)交互的核心函數(shù)。
1.5.1 driver_attach()函數(shù)
函數(shù)driver_attach()返回bus_for_each_dev()函數(shù)的運(yùn)行結(jié)果。bus_for_each_dev()函數(shù)的原型如下：
int bus_for_each_dev(struct bus_type *bus, struct device *start, void *data,
int (*fn) (struct device *, void *));
該函數(shù)迭代了在總線上的每個(gè)設(shè)備，將相關(guān)的device結(jié)構(gòu)傳遞給fn，同時(shí)傳遞data值。如果start是NULL，將從總線上的第一個(gè)設(shè)備開(kāi)始迭代；否則將從start后的第一個(gè)設(shè)備開(kāi)始迭代。如果fn返回一個(gè)非零值，將停止迭代，而這個(gè)值也會(huì)從該函數(shù)返回（摘自<<Linux設(shè)備驅(qū)動(dòng)程序>>第三版）。
該函數(shù)是如何知道總線上的每個(gè)設(shè)備的呢？在設(shè)備注冊(cè)過(guò)程中，我會(huì)詳細(xì)介紹。
/*
* drivers/base/dd.c - The core device/driver interactions.
*
* This file contains the (sometimes tricky) code that controls the
* interactions between devices and drivers, which primarily includes
* driver binding and unbinding.
*/
/**
* driver_attach - try to bind driver to devices.
* @drv: driver.
*
* Walk the list of devices that the bus has on it and try to
* match the driver with each one. If driver_probe_device()
* returns 0 and the @dev->driver is set, we've found a
* compatible pair.
*/
int driver_attach(struct device_driver * drv)
{
return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
}
1.5.2 __driver_attach()函數(shù)
函數(shù)__driver_attach()在調(diào)用driver_probe_device()函數(shù)前，需要進(jìn)行線程間的互斥處理。
static int __driver_attach(struct device * dev, void * data)
{
struct device_driver * drv = data;
/*
* Lock device and try to bind to it. We drop the error
* here and always return 0, because we need to keep trying
* to bind to devices and some drivers will return an error
* simply if it didn't support the device.
*
* driver_probe_device() will spit a warning if there
* is an error.
*/
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
down(&dev->sem);
if (!dev->driver)
driver_probe_device(drv, dev);
up(&dev->sem);
if (dev->parent)
up(&dev->parent->sem);
return 0;
}
1.5.3 driver_probe_device()函數(shù)
在driver_probe_device()函數(shù)中，調(diào)用了match函數(shù)platform_match()，如果它返回0，表示驅(qū)動(dòng)與設(shè)備不一致，函數(shù)返回；否則，調(diào)用really_probe()函數(shù)。
/**
* driver_probe_device - attempt to bind device & driver together
* @drv: driver to bind a device to
* @dev: device to try to bind to the driver
*
* First, we call the bus's match function, if one present, which should
* compare the device IDs the driver supports with the device IDs of the
* device. Note we don't do this ourselves because we don't know the
* format of the ID structures, nor what is to be considered a match and
* what is not.
*
* This function returns 1 if a match is found, an error if one occurs
* (that is not -ENODEV or -ENXIO), and 0 otherwise.
*
* This function must be called with @dev->sem held. When called for a
* USB interface, @dev->parent->sem must be held as well.
*/
int driver_probe_device(struct device_driver * drv, struct device * dev)
{
struct stupid_thread_structure *data;
struct task_struct *probe_task;
int ret = 0;
if (!device_is_registered(dev))
return -ENODEV;
if (drv->bus->match && !drv->bus->match(dev, drv))
goto done;
pr_debug("%s: Matched Device %s with Driver %s\n",
drv->bus->name, dev->bus_id, drv->name);
data = kmalloc(sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->drv = drv;
data->dev = dev;
if (drv->multithread_probe) {
probe_task = kthread_run(really_probe, data,
"probe-%s", dev->bus_id);
if (IS_ERR(probe_task))
ret = really_probe(data);
} else
ret = really_probe(data);
if (dev->bus->probe) {
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) {
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}
//設(shè)備與驅(qū)動(dòng)綁定后，對(duì)系統(tǒng)中已注冊(cè)的組件進(jìn)行事件通知。
driver_bound(dev);
ret = 1;
pr_debug("%s: Bound Device %s to Driver %s\n",
drv->bus->name, dev->bus_id, drv->name);
goto done;
if (ret != -ENODEV && ret != -ENXIO) {
/* driver matched but the probe failed */
printk(KERN_WARNING
"%s: probe of %s failed with error %d\n",
drv->name, dev->bus_id, ret);
}
/*
* Ignore errors returned by ->probe so that the next driver can try
* its luck.
*/
ret = 0;
done:
kfree(data);
atomic_dec(&probe_count);
wake_up(&probe_waitqueue);
return ret;
}
/**
* 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);
/*
* If the driver is a module, we are probably in
* the module unload path, and we want to wait
* for everything to unload before we can actually
* finish the unload.
*/
if (drv->owner)
wait_for_completion(&drv->unloaded);
}
2.4 bus_remove_driver()函數(shù)
/**
* 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;
2.5 driver_detach()函數(shù)
/**
* driver_detach - detach driver from all devices it controls.
* @drv: driver.
*/
void driver_detach(struct device_driver * drv)
{
struct device * dev;
for (;;) {
spin_lock(&drv->klist_devices.k_lock);
if (list_empty(&drv->klist_devices.k_list)) {
spin_unlock(&drv->klist_devices.k_lock);
break;
}
dev = list_entry(drv->klist_devices.k_list.prev,
struct device, knode_driver.n_node);
get_device(dev);
spin_unlock(&drv->klist_devices.k_lock);
if (dev->parent) /* Needed for USB */
down(&dev->parent->sem);
down(&dev->sem);
if (dev->driver == drv)
__device_release_driver(dev);
up(&dev->sem);
if (dev->parent)
up(&dev->parent->sem);
put_device(dev);
}
}
2.6 __device_release_driver()函數(shù)
/**
* device_release_driver - manually detach device from driver.
* @dev: device.
*
* Manually detach device from driver.
*
* __device_release_driver() must be called with @dev->sem held.
* When called for a USB interface, @dev->parent->sem must be held
* as well.
*/
for (i = 0; i < pdev->num_resources; i++) {
struct resource *p, *r = &pdev->resource;
if (r->name == NULL)
r->name = pdev->dev.bus_id;
p = r->parent;
if (!p) {
if (r->flags & IORESOURCE_MEM)
p = &iomem_resource;
else if (r->flags & IORESOURCE_IO)
p = &ioport_resource;
}
if (p && insert_resource(p, r)) {
printk(KERN_ERR
"%s: failed to claim resource %d\n",
pdev->dev.bus_id, i);
ret = -EBUSY;
goto failed;
}
}
pr_debug("Registering platform device '%s'. Parent at %s\n",
pdev->dev.bus_id, pdev->dev.parent->bus_id);
ret = device_add(&pdev->dev);
if (ret == 0)
return ret;
failed:
while (--i >= 0)
if (pdev->resource.flags & (IORESOURCE_MEM|IORESOURCE_IO))
release_resource(&pdev->resource);
return ret;
}
EXPORT_SYMBOL_GPL(platform_device_add);
3.3 device_add()函數(shù)
在文件drivers/base/core.c中實(shí)現(xiàn)了device_add()函數(shù)。
/**
* device_add - add device to device hierarchy.
* @dev: device.
*
* This is part 2 of device_register(), though may be called
* separately _iff_ device_initialize() has been called separately.
*
* This adds it to the kobject hierarchy via kobject_add(), adds it
* to the global and sibling lists for the device, then
* adds it to the other relevant subsystems of the driver model.
*/
int device_add(struct device *dev)
{
struct device *parent = NULL;
char *class_name = NULL;
struct class_interface *class_intf;
int error = -EINVAL;
dev = get_device(dev);
if (!dev || !strlen(dev->bus_id))
goto Error;
pr_debug("DEV: registering device: ID = '%s'\n", dev->bus_id);
parent = get_device(dev->parent);
error = setup_parent(dev, parent);
if (error)
goto Error;
/* first, register with generic layer. */
kobject_set_name(&dev->kobj, "%s", dev->bus_id);
error = kobject_add(&dev->kobj);
if (error)
goto Error;
/* notify platform of device entry */
if (platform_notify)
platform_notify(dev);
/* notify clients of device entry (new way) */
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->bus_notifier,
BUS_NOTIFY_ADD_DEVICE, dev);
if (dev->class) {
sysfs_create_link(&dev->kobj, &dev->class->subsys.kset.kobj,
"subsystem");
/* If this is not a "fake" compatible device, then create the
* symlink from the class to the device. */
if (dev->kobj.parent != &dev->class->subsys.kset.kobj)
sysfs_create_link(&dev->class->subsys.kset.kobj,
&dev->kobj, dev->bus_id);
if (parent) {
sysfs_create_link(&dev->kobj, &dev->parent->kobj,
"device");
#ifdef CONFIG_SYSFS_DEPRECATED
class_name = make_class_name(dev->class->name,
&dev->kobj);
if (class_name)
sysfs_create_link(&dev->parent->kobj,
&dev->kobj, class_name);
#endif
}
}
if ((error = device_add_attrs(dev)))
goto AttrsError;
if ((error = device_add_groups(dev)))
goto GroupError;
if ((error = device_pm_add(dev)))
goto PMError;
if ((error = bus_add_device(dev)))
goto BusError;
if (!dev->uevent_suppress)
kobject_uevent(&dev->kobj, KOBJ_ADD);
if ((error = bus_attach_device(dev)))
goto AttachError;
if (parent)
klist_add_tail(&dev->knode_parent, &parent->klist_children);
if (dev->class) {
down(&dev->class->sem);
/* tie the class to the device */
list_add_tail(&dev->node, &dev->class->devices);
/* notify any interfaces that the device is here */
list_for_each_entry(class_intf, &dev->class->interfaces, node)
if (class_intf->add_dev)
class_intf->add_dev(dev, class_intf);
up(&dev->class->sem);
}
Done:
kfree(class_name);
put_device(dev);
return error;
AttachError:
bus_remove_device(dev);
BusError:
device_pm_remove(dev);
PMError:
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->bus_notifier,
BUS_NOTIFY_DEL_DEVICE, dev);
device_remove_groups(dev);
GroupError:
device_remove_attrs(dev);
AttrsError:
if (dev->devt_attr) {
device_remove_file(dev, dev->devt_attr);
kfree(dev->devt_attr);
}
if (dev->class) {
sysfs_remove_link(&dev->kobj, "subsystem");
/* If this is not a "fake" compatible device, remove the
* symlink from the class to the device. */
if (dev->kobj.parent != &dev->class->subsys.kset.kobj)
sysfs_remove_link(&dev->class->subsys.kset.kobj,
dev->bus_id);
if (parent) {
#ifdef CONFIG_SYSFS_DEPRECATED
char *class_name = make_class_name(dev->class->name,
&dev->kobj);
if (class_name)
sysfs_remove_link(&dev->parent->kobj,
class_name);
kfree(class_name);
#endif
sysfs_remove_link(&dev->kobj, "device");
}
down(&dev->class->sem);
/* notify any interfaces that the device is now gone */
list_for_each_entry(class_intf, &dev->class->interfaces, node)
if (class_intf->remove_dev)
class_intf->remove_dev(dev, class_intf);
/* remove the device from the class list */
list_del_init(&dev->node);
up(&dev->class->sem);
}
ueventattrError:
device_remove_file(dev, &dev->uevent_attr);
attrError:
kobject_uevent(&dev->kobj, KOBJ_REMOVE);
kobject_del(&dev->kobj);
Error:
if (parent)
put_device(parent);
goto Done;
}
3.4 bus_attach_device()函數(shù)
在文件drivers/base/bus.c中實(shí)現(xiàn)了bus_attach_device()函數(shù)。
/**
* bus_attach_device - add device to bus
* @dev: device tried to attach to a driver
*
* - 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) {
dev->is_registered = 1;
ret = device_attach(dev);
if (ret >= 0) {
//將設(shè)備信息存儲(chǔ)在bus結(jié)構(gòu)中。在驅(qū)動(dòng)注冊(cè)后，利用bus_for_each_dev()函數(shù)可以得到所有設(shè)備的
//信息，完成驅(qū)動(dòng)與設(shè)備之間的綁定。
klist_add_tail(&dev->knode_bus, &bus->klist_devices);
ret = 0;
} else
dev->is_registered = 0;
}
return ret;
}
3.5 dd.c文件
在文件drivers/base/dd.c中實(shí)現(xiàn)了device_attach()函數(shù)。
3.5.1 device_attach()函數(shù)
/**
* device_attach - try to attach device to a driver.
* @dev: device.
*
* Walk the list of drivers that the bus has and call
* driver_probe_device() for each pair. If a compatible
* pair is found, break out and return.
*
* Returns 1 if the device was bound to a driver;
* 0 if no matching device was found; error code otherwise.
*
* When called for a USB interface, @dev->parent->sem must be held.
*/
int device_attach(struct device * dev)
{
int ret = 0;
down(&dev->sem);
if (dev->driver) {
ret = device_bind_driver(dev);
if (ret == 0)
ret = 1;
} else
ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
up(&dev->sem);
return ret;
}
static int __device_attach(struct device_driver * drv, void * data)
{
struct device * dev = data;
//在此之后，利用驅(qū)動(dòng)信息來(lái)探測(cè)設(shè)備，參考第一部分的介紹
return driver_probe_device(drv, dev);
}
3.5.2 device_bind_driver()函數(shù)
/**
* device_bind_driver - bind a driver to one device.
* @dev: device.
*
* Allow manual attachment of a driver to a device.
* Caller must have already set @dev->driver.
*
* Note that this does not modify the bus reference count
* nor take the bus's rwsem. Please verify those are accounted
* for before calling this. (It is ok to call with no other effort
* from a driver's probe() method.)
*
* This function must be called with @dev->sem held.
*/
int device_bind_driver(struct device *dev)
{
int ret;
ret = driver_sysfs_add(dev);
if (!ret)
driver_bound(dev); //通知鏈
return ret;
}
