From cornelia.huck@de.ibm.com Thu Sep 11 02:38:07 2008 From: Cornelia Huck Date: Wed, 3 Sep 2008 18:26:40 +0200 Subject: Driver core: Clarify device cleanup. To: Greg K-H Message-ID: <20080903182640.14279526@gondolin.boeblingen.de.ibm.com> From: Cornelia Huck Make the comments on how to use device_initialize(), device_add() and device_register() a bit clearer - in particular, explicitly note that put_device() must be used once we tried to add the device to the hierarchy. Signed-off-by: Cornelia Huck Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -523,11 +523,16 @@ static void klist_children_put(struct kl * device_initialize - init device structure. * @dev: device. * - * This prepares the device for use by other layers, - * including adding it to the device hierarchy. + * This prepares the device for use by other layers by initializing + * its fields. * It is the first half of device_register(), if called by - * that, though it can also be called separately, so one - * may use @dev's fields (e.g. the refcount). + * that function, though it can also be called separately, so one + * may use @dev's fields. In particular, get_device()/put_device() + * may be used for reference counting of @dev after calling this + * function. + * + * NOTE: Use put_device() to give up your reference instead of freeing + * @dev directly once you have called this function. */ void device_initialize(struct device *dev) { @@ -835,9 +840,13 @@ static void device_remove_sys_dev_entry( * 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 + * This adds @dev 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. + * + * NOTE: _Never_ directly free @dev after calling this function, even + * if it returned an error! Always use put_device() to give up your + * reference instead. */ int device_add(struct device *dev) { @@ -965,6 +974,10 @@ done: * I.e. you should only call the two helpers separately if * have a clearly defined need to use and refcount the device * before it is added to the hierarchy. + * + * NOTE: _Never_ directly free @dev after calling this function, even + * if it returned an error! Always use put_device() to give up the + * reference initialized in this function instead. */ int device_register(struct device *dev) {