DEVFS_CLEAN(9F) Kernel Functions for Drivers DEVFS_CLEAN(9F)

NAME

devfs_clean - destroy unreferenced devfs nodes and detach devices

SYNOPSIS

#include <sys/fs/dv_node.h>

int
devfs_clean(dev_info_t *dip, char *devnm, uint_t flags);

INTERFACE LEVEL

Volatile - private DDI function

This is a private function that is not part of the stable DDI. It may
be removed or changed at any time.

PARAMETERS

dip A pointer to the device's dev_info structure. Clean up is
rooted at this device.

devnm An optional character string used to restrict the devfs nodes
list.

flags The following flag is supported:

DV_CLEAN_FORCE force clean of referenced directories,
referenced empty directories are marked as
stale to facilitate DR (dynamic
reconfiguration)

DESCRIPTION

The devfs_clean() function is used to clean up and detach devices from
the system. While many device drivers may have one or more minor nodes
created with ddi_create_minor_node(9F), some device drivers may have
children devices with different device drivers attached. Each of these
entries shows up in the file system of the global zone under /devices
(see devfs(4FS)). These nodes are referred to as a devfs nodes
(dv_node).

devfs caches unreferenced devfs nodes to speed up the performance of
ls, find, etc. The devfs_clean() function is used to cleanup cached
nodes to reclaim memory as well as to facilitate device removal (devfs
nodes reference dev_info nodes, which prevents driver from detaching).

The devfs_clean() function starts searching the tree rooted at dip.
All directories encountered are recursed through. If devnm is not
NULL, then it is used to limit the nodes that it searches. It compares
the name of the node, ignoring any part of the device's name that
corresponds to a minor node. If devnm has been specified, then cleanup
stops immediately after a busy devfs node has been encountered.

Not all nodes may be cleaned up when a driver calls the devfs_clean()
function. However, this is a non-fatal situation. Callers should
continue trying to offline devices as many holds from userland
processes may exist due to device contracts which will be released when
the device is offlined.

If a shell parks in a /devices directory, the devfs node will be held,
preventing the corresponding device to be detached. This would be a
denial of service against DR (dynamic reconfiguration). To prevent
this, DR code calls devfs_clean() with the DV_CLEAN_FORCE flag.

CONTEXT

This function may be called in user or kernel context.

RETURN VALUES

The devfs_clean() function always succeeds and returns zero.

SEE ALSO

devfs(4FS)

illumos July 26, 2016 illumos