Re: [PATCH 2/6] virtio: add register_virtio_root_device()
From: Cornelia Huck <hidden>
Date: 2008-12-11 12:59:24
On Wed, 10 Dec 2008 17:45:35 +0000, Mark McLoughlin [off-list ref] wrote:
Add a function to allocate a root device object to group the devices from a given virtio implementation. Also add a 'module' sysfs symlink to allow so that userspace can generically determine which virtio implementation a device is associated with. This will be used by Fedora mkinitrd to generically determine e.g. that virtio_pci is needed to mount a given root filesystem.
Nothing about this is really virtio-specific (just as s390_root_dev_register() is not really s390-specific), and a 'module' symlink doesn't really hurt in a generic implementation, even if it is unneeded. I'm voting to put this in some generic, always built-in code (or have the users select it) so we could also use it from s390.
quoted hunk
Signed-off-by: Mark McLoughlin <redacted> --- drivers/virtio/virtio.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/virtio.h | 10 ++++++ 2 files changed, 81 insertions(+), 0 deletions(-)diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index 018c070..61e6597 100644 --- a/drivers/virtio/virtio.c +++ b/drivers/virtio/virtio.c@@ -1,6 +1,7 @@ #include <linux/virtio.h> #include <linux/spinlock.h> #include <linux/virtio_config.h> +#include <linux/err.h> /* Unique numbering for virtio devices. */ static unsigned int dev_index;@@ -200,6 +201,76 @@ void unregister_virtio_device(struct virtio_device *dev) } EXPORT_SYMBOL_GPL(unregister_virtio_device); +/* A root device for virtio devices from a given backend. This makes them + * appear as /sys/devices/{name}/0,1,2 not /sys/devices/0,1,2. It also allows + * us to have a /sys/devices/{name}/module symlink to the backend module. */ +struct virtio_root_device +{ + struct device dev; + struct module *owner; +}; + +static struct virtio_root_device *to_virtio_root(struct device *dev) +{ + return container_of(dev, struct virtio_root_device, dev); +} + +static void release_virtio_root_device(struct device *dev) +{ + struct virtio_root_device *root = to_virtio_root(dev); + if (root->owner) + sysfs_remove_link(&root->dev.kobj, "module"); + kfree(root); +}
Can this code be a module? If yes, move the release callback to a build-in as there are races with release-functions in modules.
+
+struct device *__register_virtio_root_device(const char *name,
+ struct module *owner)
+{
+ struct virtio_root_device *root;
+ int err = -ENOMEM;
+
+ root = kzalloc(sizeof(struct virtio_root_device), GFP_KERNEL);
+ if (!root)
+ goto out;
+
+ err = dev_set_name(&root->dev, name);
+ if (err)
+ goto free_root;
+
+ err = device_register(&root->dev);
+ if (err)
+ goto free_root;
+
+ root->dev.parent = NULL;
+ root->dev.release = release_virtio_root_device;You must set ->release before calling device_register(), and setting the parent is unneeded.
+
+ 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;
+
+free_root:
+ kfree(root);You need to call device_put() if you called device_register().
quoted hunk
+out: + return ERR_PTR(err); +} +EXPORT_SYMBOL_GPL(__register_virtio_root_device); + +void unregister_virtio_root_device(struct device *root) +{ + device_unregister(root); +} +EXPORT_SYMBOL_GPL(unregister_virtio_root_device); + static int virtio_init(void) { if (bus_register(&virtio_bus) != 0)diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 06005fa..66e6c67 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h@@ -93,6 +93,16 @@ struct virtio_device int register_virtio_device(struct virtio_device *dev); void unregister_virtio_device(struct virtio_device *dev); +/* A root device is a dummy device used to group virtio devices from each + * implementation. */ +struct device *__register_virtio_root_device(const char *name, + struct module *owner); +static inline struct device *register_virtio_root_device(const char *name) +{ + return __register_virtio_root_device(name, THIS_MODULE); +} +void unregister_virtio_root_device(struct device *root); + /** * virtio_driver - operations for a virtio I/O driver * @driver: underlying device driver (populate name and owner).-- 1.5.4.3