Tribblix: manual page: ddi_get

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

NAME

ddi_get_devstate - Check device state

SYNOPSIS

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

ddi_devstate_t ddi_get_devstate(dev_info_t *dip);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

dip
Pointer to the device's dev_info structure

DESCRIPTION

The ddi_get_devstate() function returns a value indicating the state
of the device specified by dip, as derived from the configuration
operations that have been performed on it (or on the bus on which it
resides) and any fault reports relating to it.

RETURN VALUES

DDI_DEVSTATE_OFFLINE
The device is offline. In this state, the
device driver is not attached, nor will it
be attached automatically. The device cannot
be used until it is brought online.

DDI_DEVSTATE_DOWN
The device is online but unusable due to a
fault.

DDI_DEVSTATE_QUIESCED
The bus on which the device resides has
been quiesced. This is not a fault, but no
operations on the device should be performed
while the bus remains quiesced.

DDI_DEVSTATE_DEGRADED
The device is online but only able to
provide a partial or degraded service, due
to a fault.

DDI_DEVSTATE_UP
The device is online and fully operational.

CONTEXT

The ddi_get_devstate() function may be called from user, kernel, or
interrupt context.

NOTES

A device driver should call this function to check its own state at
each major entry point, and before committing resources to a
requested operation. If a driver discovers that its device is
already down, it should perform required cleanup actions and return
as soon as possible. If appropriate, it should return an error to
its caller, indicating that the device has failed (for example, a
driver's read(9E) routine would return EIO).

Depending on the driver, some non-I/O operations (for example, calls
to the driver's ioctl(9E) routine) may still succeed; only functions
which would require fully accessible and operational hardware will
necessarily fail. If the bus on which the device resides is quiesced,
the driver may return a value indicating the operation should be
retried later (for example, EAGAIN). Alternatively, for some classes
of device, it may be appropriate for the driver to enqueue the
operation and service it once the bus has been unquiesced. Note that
not all busses support the quiesce/unquiesce operations, so this
value may never be seen by some drivers.