* Kirti Wankhede <kwankh...@nvidia.com> [2016-11-09 02:36:12 +0530]:
[...]
> >> +/*
> >> + * mdev_register_device : Register a device
> >> + * @dev: device structure representing parent device.
> >> + * @ops: Parent device operation structure to be registered.
> >> + *
> >> + * Add device to list of registered parent devices.
> >> + * Returns a negative value on error, otherwise 0.
> >> + */
> >> +int mdev_register_device(struct device *dev, const struct parent_ops *ops)
> >> +{
> >> + int ret;
> >> + struct parent_device *parent;
> >> +
> >> + /* check for mandatory ops */
> >> + if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups)
> >> + return -EINVAL;
> >> +
> >> + dev = get_device(dev);
> >> + if (!dev)
> >> + return -EINVAL;
> >> +
> >> + mutex_lock(&parent_list_lock);
> >> +
> >> + /* Check for duplicate */
> >> + parent = __find_parent_device(dev);
> >> + if (parent) {
> >> + ret = -EEXIST;
> >> + goto add_dev_err;
> >> + }
> >> +
> >> + parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> >> + if (!parent) {
> >> + ret = -ENOMEM;
> >> + goto add_dev_err;
> >> + }
> >> +
> >> + kref_init(&parent->ref);
> >> + mutex_init(&parent->lock);
> >> +
> >> + parent->dev = dev;
> >> + parent->ops = ops;
> >> +
> >> + if (!mdev_bus_compat_class) {
> >> + mdev_bus_compat_class = class_compat_register("mdev_bus");
> >> + if (!mdev_bus_compat_class) {
> >> + ret = -ENOMEM;
> >> + goto add_dev_err;
> >> + }
> >> + }
> >> +
> >> + ret = parent_create_sysfs_files(parent);
> >> + if (ret)
> >> + goto add_dev_err;
> >> +
> >> + ret = class_compat_create_link(mdev_bus_compat_class, dev, NULL);
> >> + if (ret)
> >> + dev_warn(dev, "Failed to create compatibility class link\n");
> >> +
> >> + list_add(&parent->next, &parent_list);
> >> + mutex_unlock(&parent_list_lock);
> >> +
> >> + dev_info(dev, "MDEV: Registered\n");
> >> + return 0;
> >> +
> >> +add_dev_err:
> >> + mutex_unlock(&parent_list_lock);
> >> + if (parent)
> >> + mdev_put_parent(parent);
> > Why do this? I don't find the place that you call mdev_get_parent above.
> >
>
> kref_init(&parent->ref);
> Above increments the ref_count, so mdev_put_parent() should be called if
> anything fails.
>
> >> + else
> >> + put_device(dev);
> > Shouldn't we always do this?
> >
>
> When mdev_put_parent() is called, its release function do this. So if
> mdev_put_parent() is called, we don't need this.
Sorry for missing that. Thanks for the explanation!
>
> >> + return ret;
> >> +}
> >> +EXPORT_SYMBOL(mdev_register_device);
> >> +
[...]
--
Dong Jia
