DETACH(9E) Driver Entry Points DETACH(9E)


detach - detach or suspend a device


#include <sys/ddi.h>
#include <sys/sunddi.h>

int prefixdetach(dev_info_t * dip, ddi_detach_cmd_t cmd);


illumos DDI specific (illumos DDI)


A pointer to the device's dev_info structure.

Type of detach; the driver should return DDI_FAILURE if any value
other than DDI_DETACH or DDI_SUSPEND is passed to it.


The detach() function complements the attach(9E) routine.

If cmd is set to DDI_DETACH, detach() is used to remove the state
associated with a given instance of a device node prior to the removal of
that instance from the system.

The detach() function will be called once for each instance of the device
for which there has been a successful attach(), once there are no longer
any opens on the device. An attached instance of a driver can be
successfully detached only once. The detach() function should clean up
any per instance data initialized in attach(9E) and call kmem_free(9F) to
free any heap allocations. For information on how to unregister interrupt
handlers, see ddi_add_intr(9F). This should also include putting the
underlying device into a quiescent state so that it will not generate

Drivers that set up timeout(9F) routines should ensure that they are
cancelled before returning DDI_SUCCESS from detach().

If detach() determines a particular instance of the device cannot be
removed when requested because of some exceptional condition, detach()
must return DDI_FAILURE, which prevents the particular device instance
from being detached. This also prevents the driver from being unloaded. A
driver instance failing the detach must ensure that no per instance data
or state is modified or freed that would compromise the system or
subsequent driver operation.

The system guarantees that the function will only be called for a
particular dev_info node after (and not concurrently with) a successful
attach(9E) of that device. The system also guarantees that detach() will
only be called when there are no outstanding open(9E) calls on the

The DDI_SUSPEND cmd is issued when the entire system is being suspended
and power removed from it or when the system must be made quiescent. It
will be issued only to devices which have a reg property or which export
a pm-hardware-state property with the value needs-suspend-resume.

If cmd is set to DDI_SUSPEND, detach() is used to suspend all activity of
a device before power is (possibly) removed from the device. The steps
associated with suspension must include putting the underlying device
into a quiescent state so that it will not generate interrupts or modify
or access memory. Once quiescence has been obtained, detach() can be
called with outstanding open(9E) requests. It must save the hardware
state of the device to memory and block incoming or existing requests
until attach() is called with DDI_RESUME.

If the device is used to store file systems, then after DDI_SUSPEND is
issued, the device should still honor dump(9E) requests as this entry
point may be used by suspend-resume operation (see cpr(4)) to save state
file. It must do this, however, without disturbing the saved hardware
state of the device.

If the device driver uses automatic device Power Management interfaces
(driver exports pm-components(9P) property), it might need to call
pm_raise_power(9F) if the current power level is lower than required to
complete the dump(9E) request.

Before returning successfully from a call to detach() with a command of
DDI_SUSPEND, the driver must cancel any outstanding timeouts and make any
driver threads quiescent.

If DDI_FAILURE is returned for the DDI_SUSPEND cmd, either the operation
to suspend the system or to make it quiescent will be aborted.


For DDI_DETACH, the state associated with the given device
was successfully removed. For DDI_SUSPEND, the driver was
successfully suspended.

The operation failed or the request was not understood.
The associated state is unchanged.


This function is called from user context only.


See attributes(7) for descriptions of the following attributes:

|Interface Stability | Committed |


cpr(4), pm(4D), attach(9E), dump(9E), open(9E), power(9E),
ddi_add_intr(9F), ddi_dev_is_needed(9F), ddi_map_regs(9F), kmem_free(9F),
pm_raise_power(9F), timeout(9F), pm(9P), pm-components(9P)

Writing Device Drivers

illumos July 25, 2015 DETACH(9E)