Entry Point Summary

Entry Points in Alphabetic Order

Entry Point	Purpose	Discussion
pfxattach	LEGO attach entry point.	(((TBS)))
pfxclose	Note the device is not in use.	page 149
pfxdevflag	Constant flag bits for driver features.	page 140
pfxdetach	LEGO detach entry point.	(((TBS)))
pfxdiag	LEGO diagnostic entry point.	(((TBS)))
pfxedtinit	Initialize driver from VECTOR statement.	page 144
pfxhalt	Prepare for system shutdown.	page 168
pfxinit	Initialize driver at load or boot time.	page 144
pfxintr	Handle device interrupt.	page 164
pfxioctl	Implement control operations.	page 150
pfxmap	Implement memory-mapping (IRIX).	page 159
pfxmmap	Implement memory-mapping (SVR4).	page 161
pfxopen	Connect a process to a device. Connect a stream module.	page 146 page 543
pfxpoll	Implement device event test.	page 156
pfxprint	Display diagnostic about block device.	page 169
pfxread	Implement device input.	page 152
pfxrput	STREAMS message on read queue.	page 544
pfxsize	Return logical size of block device.	page 169
pfxsrv	STREAMS service queued messages.	page 545
pfxstart	Initialize driver with interrupts enabled.	page 145
pfxstrategy	Input/output for a block device.	page 154
pfxunload	Prepare loadable module for unloading.	page 167
pfxunmap	Undo pfxmmap memory mapping.	page 162
pfxwput	STREAMS message on write queue.	page 544
pfxwrite	Implement device output.	page 152

The use of entry points in different types of drivers is summarized in Table 8-2. The columns of Table 8-2 show the different types of drivers. The table cells show whether a given entry point is optional (O), required (R), or not allowed (N).

Use of Driver Entry Points

Entry Point	Character	Block	Pseudo	STREAMS
pfxattach	O	O	O	O
pfxclose	R	R	R	R
pfxdetach	O	O	O	O
pfxdevflag	O	O	O	O
pfxdiag	O	O	O	O
pfxedtinit	O	O	N	N
pfxhalt	O	O	O	O
pfxinit	O	O	O	O
pfxintr	O	O	N	N
pfxioctl	O	O	O	N
pfxmap	O	O	O	N
pfxmmap	O	O	O	N
pfxopen	R	R	R	R
pfxpoll	O	O	N	O
pfxprint	N	O	N	N
pfxread	O	N	O	N
pfxrput	N	N	N	R
pfxsize	N	R	N	N
pfxsrv	N	N	N	R
pfxstart	O	O	O	O
pfxstrategy	N	R	N	N
pfxunload	O	O	O	O
pfxunmap	O	O	O	N
pfxwput	N	N	N	R
pfxwrite	O	N	O	N

As can be seen from Table 8-2, no driver supports all entry points.

• A minimal driver for a character device supports pfxinit(), pfxopen(), pfxread(), pfxwrite(), and pfxclose(). The pfxioctl() and pfxpoll() entry points are optional.

• A minimal pseudo-device driver supports pfxstart(), pfxopen(), pfxmap(), pfxunmap(), and pfxclose() (the latter two as stubs).

• A minimal block device driver supports pfxedtinit(), pfxopen(), pfxsize(), pfxstrategy(), and pfxclose().