device_get_state9freebsd

Usage

Overview

The current state of a device is accessed by calling device_get_state() which returns DS_NOTPRESENT, DS_ALIVE, DS_ATTACHED or DS_BUSY (described in device(9)). To test see if a device was successfully probed, call device_is_alive() which simply returns if the state is greater or equal to DS_ALIVE. To test see if a device was successfully attached, call device_is_attached() which simply returns if the state is greater or equal to DS_ATTACHED.

Each device has a busy count which is incremented when device_busy() is called and decremented when device_unbusy() is called. Both routines return an error if the device state is less than DS_ATTACHED.

When device_busy() is called on a device in the DS_ATTACHED state, the device changes to the DS_BUSY state. When device_unbusy() is called and after decrementing, the busy count for the device is zero, the device changes to the DS_ATTACHED state.