Re: [PATCH 1/4] driver core: add root_device_register()

Mark McLoughlin
2008-12-12T08:58:40Z

On Fri, 2008-12-12 at 09:42 +0100, Cornelia Huck wrote:
> On Thu, 11 Dec 2008 18:23:27 +0000,
> Mark McLoughlin <markmc@redhat.com> wrote:
>
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index 8c2cc26..20e5825 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1196,6 +1196,93 @@ 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;
> > +};
> > +
> > +static void root_device_release(struct device *dev)
> > +{
>
> You need to get the root device here and free that.
>
> > + kfree(dev);
> > +}

Yeah, I just figured it was a little overkill given the structure
definition is three lines away. Here it is, though.

Cheers,
Mark.

From: Mark McLoughlin <markmc@redhat.com>
Subject: [PATCH] driver core: add root_device_register()

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>
---
drivers/base/core.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/device.h | 11 ++++++
2 files changed, 100 insertions(+), 0 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 8c2cc26..05320af 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1196,6 +1196,95 @@ 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);
+ }
+
+ 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;
+ }
+
+ 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)
{
diff --git a/include/linux/device.h b/include/linux/device.h
index 1a3686d..9e02980 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -483,6 +483,17 @@ 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.
*/
--
1.6.0.3