man pages section 9: DDI and DKI Driver Entry Points

Exit Print View

Updated: July 2014



detach - detach or suspend a device


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

int prefix detach(dev_info_t dip, ddi_detach_cmd_t cmd);

Interface Level

Solaris DDI specific (Solaris 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 interrupts.

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 device.


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(7)) 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.

Return Values


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(5) for descriptions of the following attributes:

Interface Stability

See also

cpr(7), pm(7D), pm(9P), pm-components(9P), attach(9E), dump(9E), open(9E), power(9E), ddi_add_intr(9F), ddi_map_regs(9F) , kmem_free(9F), pm_raise_power (9F), timeout(9F)

Writing Device Drivers for Oracle Solaris 11.2