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driver core: add root_device_register()

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Add support for allocating root device objects which group
device objects under /sys/devices directories.

Also add a sysfs 'module' symlink which points to the owner
of the root device object. This symlink will be used in virtio
to allow userspace to determine which virtio bus implementation
a given device is associated with.

[Includes suggestions from Cornelia Huck]

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Mark McLoughlin 2008-12-15 12:58:26 +00:00 committed by Greg Kroah-Hartman
parent 7232800ba8
commit 0aa0dc41bf
2 changed files with 102 additions and 0 deletions
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91
drivers/base/core.c
View File

@ -1217,6 +1217,97 @@ EXPORT_SYMBOL_GPL(put_device);
EXPORT_SYMBOL_GPL(device_create_file);
EXPORT_SYMBOL_GPL(device_remove_file);
struct root_device
{
struct device dev;
struct module *owner;
};
#define to_root_device(dev) container_of(dev, struct root_device, dev)
static void root_device_release(struct device *dev)
{
kfree(to_root_device(dev));
}
/**
* __root_device_register - allocate and register a root device
* @name: root device name
* @owner: owner module of the root device, usually THIS_MODULE
*
* This function allocates a root device and registers it
* using device_register(). In order to free the returned
* device, use root_device_unregister().
*
* Root devices are dummy devices which allow other devices
* to be grouped under /sys/devices. Use this function to
* allocate a root device and then use it as the parent of
* any device which should appear under /sys/devices/{name}
*
* The /sys/devices/{name} directory will also contain a
* 'module' symlink which points to the @owner directory
* in sysfs.
*
* Note: You probably want to use root_device_register().
*/
struct device *__root_device_register(const char *name, struct module *owner)
{
struct root_device *root;
int err = -ENOMEM;
root = kzalloc(sizeof(struct root_device), GFP_KERNEL);
if (!root)
return ERR_PTR(err);
err = dev_set_name(&root->dev, name);
if (err) {
kfree(root);
return ERR_PTR(err);
}
root->dev.release = root_device_release;
err = device_register(&root->dev);
if (err) {
put_device(&root->dev);
return ERR_PTR(err);
}
#ifdef CONFIG_MODULE /* gotta find a "cleaner" way to do this */
if (owner) {
struct module_kobject *mk = &owner->mkobj;
err = sysfs_create_link(&root->dev.kobj, &mk->kobj, "module");
if (err) {
device_unregister(&root->dev);
return ERR_PTR(err);
}
root->owner = owner;
}
#endif
return &root->dev;
}
EXPORT_SYMBOL_GPL(__root_device_register);
/**
* root_device_unregister - unregister and free a root device
* @root: device going away.
*
* This function unregisters and cleans up a device that was created by
* root_device_register().
*/
void root_device_unregister(struct device *dev)
{
struct root_device *root = to_root_device(dev);
if (root->owner)
sysfs_remove_link(&root->dev.kobj, "module");
device_unregister(dev);
}
EXPORT_SYMBOL_GPL(root_device_unregister);
static void device_create_release(struct device *dev)
{

11
include/linux/device.h
View File

@ -482,6 +482,17 @@ extern struct device *device_find_child(struct device *dev, void *data,
extern int device_rename(struct device *dev, char *new_name);
extern int device_move(struct device *dev, struct device *new_parent);
/*
* Root device objects for grouping under /sys/devices
*/
extern struct device *__root_device_register(const char *name,
struct module *owner);
static inline struct device *root_device_register(const char *name)
{
return __root_device_register(name, THIS_MODULE);
}
extern void root_device_unregister(struct device *root);
/*
* Manual binding of a device to driver. See drivers/base/bus.c
* for information on use.