Some operations can be performed by any type of driver, such as the functions that are required for module loading and for the required autoconfiguration entry points. This section discusses types of entry points that are common to all drivers. The common entry points are listed in Summary of Common Entry Points with links to man pages and other relevant discussions.
Drivers for character and block devices export the cb_ops(9S) structure, which defines the driver entry points for block device access and character device access. Both types of drivers are required to support the open(9E) and close(9E) entry points. Block drivers are required to support strategy(9E), while character drivers can choose to implement whatever mix of read(9E), write(9E), ioctl(9E), mmap(9E), or devmap(9E) entry points is appropriate for the type of device. Character drivers can also support a polling interface through chpoll(9E). Asynchronous I/O is supported through aread(9E) and awrite(9E) for block drivers and those drivers that can use both block and character file systems.
All drivers are required to implement the loadable module entry points _init(9E), _fini(9E), and _info(9E) to load, unload, and report information about the driver module.
Drivers should allocate and initialize any global resources in _init(9E). Drivers should release their resources in _fini(9E).
Drivers are required to implement the attach(9E), detach(9E), and getinfo(9E) entry points for device autoconfiguration. Drivers can also implement the optional entry point probe(9E) in cases where devices do not identify themselves during boot-up, such as SCSI target devices. See Chapter 6, Driver Autoconfiguration for more information on these routines.
The Oracle Solaris platform provides a rich set of interfaces to maintain and export kernel-level statistics, also known as kstats. Drivers are free to use these interfaces to export driver and device statistics that can be used by user applications to observe the internal state of the driver. Two entry points are provided for working with kernel statistics:
ks_snapshot(9E) captures kstats at a specific time.
ks_update(9E) can be used to update kstat data at will. ks_update() is useful in situations where a device is set up to track kernel data but extracting that data is time-consuming.
For further information, see the kstat_create(9F) and kstat(9S) man pages. See also Kernel Statistics.
Drivers for hardware devices that provide Power Management functionality can support the optional power(9E) entry point. See Chapter 12, Power Management for details about this entry point.
A driver that manages devices must implement the quiesce(9E) entry point. Drivers that do not manage devices can set the devo_quiesce field in the dev_ops structure to ddi_quiesce_not_needed(). The quiesce() function can be called only when the system is single-threaded at high PIL (priority interrupt level) with preemption disabled. Therefore, this function must not be blocked. If a device has a defined reset state configuration, the driver should return that device to that reset state as part of the quiesce operation. An example of this case is Fast Reboot, where firmware is bypassed when booting to a new operating system image.
The following table lists entry points that can be used by all types of drivers.
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