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unlink() callback

Called to check if a node is unlinked from the namespace

Synopsis:

#include <sys/pmm.h>

int unlink(void *data, int nlink, unsigned flags);

libc

This function is called to check whether the policy will allow a node to be unlinked from the namespace:

data

Policy specific data returned by the create() function when the node was created.

nlink

Link count for the namespace:

flags

0, or a combination of the following:

PMM_NODE_CLIENT: Node was created by a client request.
If this flag is not set, it is created by the power manager.
PMM_NODE_DETACH: Driver responsible for the node's power mode has just detached.
If this flag is not set, the unlink is being performed by an explicit unlink request (via the resmgr interface or by pmm_node_unlink())

The unlink() function is called from the following:

pmm_node_unlink(). In this case, flags is 0 or PMM_NODE_CLIENT.
the resmgr unlink handler. In this case, flags is 0 or PMM_NODE_CLIENT.
the resmgr close handler when the driver responsible for the node's power modes detaches.
In this case, flags is PMM_NODE_DETACH set, and may also have PMM_NODE_CLIENT set if the node was created by a client request

If the policy will allow the unlink, it should return EOK:

on return from this function, the specified node will be unlinked, and if there are no client references, it will be automatically deleted and the destroy() function called to clean up policy specific data for the node.
if the node is a non-empty directory, all nodes below it will also be unlinked.
Any nodes that have no client references will automatically be deleted, and the destroy() function called to clean up policy specific data for the node.
any nodes that have client references remain in existence until the last client detaches. They will not be visible from the name space, so no new client references can be created.

Otherwise, it should return EBUSY, and the unlink operation will fail.

The default action (if the unlink() function is not overriden) is to allow: