Linking and testing SCO OpenServer 5 drivers

Configuring interrupt handlers

The six different types of interrupt handling that can be used by a device driver are listed on the sdevice(F) manual page. These types can be divided into three basic groups according to the capabilities of the device being controlled and how the driver handles this:

type 0: The device does not use an interrupt request line (IRQ) or the driver registers the IRQ dynamically when it initializes.
types 1 and 2: The driver uses an IRQ exclusively for itself although it may share this among several devices that it controls.
types 3, 4 and 5: The driver can share an IRQ between devices. Note that the number of devices that can share a single IRQ is determined by the NSHINTR tunable parameter. The default value for this parameter is 8 but it can be set as high as 20. NSHINTR is accessed through the configure utility, under Miscellaneous device driver and hardware parameters.

If interrupts are used, you need to decide how the vector is installed. There are three possibilities:

The IRQ is statically configured into the Link Kit.
The IRQ is statically configured into the Link Kit and is also registered by the driver.
The IRQ is registered dynamically by the driver (preferred method). See ``Interrupt handlers, attaching and registering'' for more information.

If a device uses a hardware interrupt line exclusively for itself, it may be necessary to change the interrupt it uses if another device uses the same interrupt. This does not apply to bus architectures, such as PCI, which support dynamically allocatable interrupts. On other bus architectures, the device controller card may have jumpers that enable the IRQ setting to be changed, or there may be a setup program available to respecify the IRQ. In some cases, it may not be possible to change the IRQ.

If interrupts are used, you also need to decide on the interrupt priority level (IPL) which is determined by the type of driver; see spl(D3oddi) for more information.

The following tables show the appropriate values to be inserted in the driver's sdevice and mdevice entry. For drivers that register their use of interrupts using add_intr_handler(D3oddi) or idistributed(D3oddi), the appropriate value of the type argument and the mode member of the driver_info structure (defined in <sys/ci/ciintr.h>) are shown respectively.

Use of IRQ installed by sdevice mdevice add_intr_handler

interrupt col 4 col 5 col 6 col 3

by driver IPL type vector chars type

Not used Link Kit only 0 0 0 Not used

Exclusive Link Kit only ipl 1,2 irq Not used

Exclusive Link Kit + driver ipl 1 irq G 1

ipl 2 irq G 2

Exclusive Driver only 0 0 0 1

0 0 0 2

Shared Link Kit only ipl 3 irq Not used

ipl 4 irq Not used

ipl 5 irq Not used

Shared Link Kit + driver ipl 3 irq G 3

ipl 4 irq G 4

ipl 5 irq G 5

Shared Driver only 0 0 0 3

0 0 0 4

0 0 0 5

Use of	IRQ installed by	sdevice	mdevice	add_intr_handler
interrupt		col 4	col 5	col 6	col 3
by driver		IPL	type	vector	chars	type
Not used	Link Kit only	0	0	0		Not used
Exclusive	Link Kit only	*ipl*	1,2	*irq*		Not used
Exclusive	Link Kit + driver	*ipl*	1	*irq*	G	1
		*ipl*	2	*irq*	G	2
Exclusive	Driver only	0	0	0		1
		0	0	0		2
Shared	Link Kit only	*ipl*	3	*irq*		Not used
		*ipl*	4	*irq*		Not used
		*ipl*	5	*irq*		Not used
Shared	Link Kit + driver	*ipl*	3	*irq*	G	3
		*ipl*	4	*irq*	G	4
		*ipl*	5	*irq*	G	5
Shared	Driver only	0	0	0		3
		0	0	0		4
		0	0	0		5

Use of IRQ installed by sdevice mdevice idistributed

interrupt col 4 col 5 col 6 col 3

by driver IPL type vector chars dip->mode

Not used Link Kit only 0 0 0 IMODE_NONE

Exclusive Link Kit only ipl 1,2 irq IMODE_NONE

Exclusive Link Kit + driver ipl 1 irq G IMODE_EXCLUSIVE

ipl 2 irq G IMODE_SHARED_DRIVER

Exclusive Driver only 0 0 0 IMODE_EXCLUSIVE

0 0 0 IMODE_SHARED_DRIVER

Shared Link Kit only ipl 3 irq IMODE_SHARED_DRIVERIPL

ipl 4 irq IMODE_SHARED_CDRIVERIPL

ipl 5 irq IMODE_SHARED_INTER

Shared Link Kit + driver ipl 3 irq G IMODE_SHARED_DRIVERIPL

ipl 4 irq G IMODE_SHARED_CDRIVERIPL

ipl 5 irq G IMODE_SHARED_INTER

Shared Driver only 0 0 0 IMODE_SHARED_DRIVERIPL

0 0 0 IMODE_SHARED_CDRIVERIPL

0 0 0 IMODE_SHARED_INTER

ipl is the interrupt priority level (IPL) for which the driver is designed. Although it is defined in sdevice(F), its value is not adjustable.

Use of	IRQ installed by	sdevice	mdevice	idistributed
interrupt		col 4	col 5	col 6	col 3
by driver		IPL	type	vector	chars	dip->mode
Not used	Link Kit only	0	0	0		IMODE_NONE
Exclusive	Link Kit only	*ipl*	1,2	*irq*		IMODE_NONE
Exclusive	Link Kit + driver	*ipl*	1	*irq*	G	IMODE_EXCLUSIVE
		*ipl*	2	*irq*	G	IMODE_SHARED_DRIVER
Exclusive	Driver only	0	0	0		IMODE_EXCLUSIVE
		0	0	0		IMODE_SHARED_DRIVER
Shared	Link Kit only	*ipl*	3	*irq*		IMODE_SHARED_DRIVERIPL
		*ipl*	4	*irq*		IMODE_SHARED_CDRIVERIPL
		*ipl*	5	*irq*		IMODE_SHARED_INTER
Shared	Link Kit + driver	*ipl*	3	*irq*	G	IMODE_SHARED_DRIVERIPL
		*ipl*	4	*irq*	G	IMODE_SHARED_CDRIVERIPL
		*ipl*	5	*irq*	G	IMODE_SHARED_INTER
Shared	Driver only	0	0	0		IMODE_SHARED_DRIVERIPL
		0	0	0		IMODE_SHARED_CDRIVERIPL
		0	0	0		IMODE_SHARED_INTER

irq is the interrupt request line (IRQ) configured for the hardware on a system. If the hardware allows the IRQ to be changed using jumpers or a setup program:

It should be possible for a customer to configure the IRQ for their system.
For a boot-time loadable driver, the IRQ should be made tunable in the Bootload file; for further information, see btld(F).
Any mkdev(ADM) script should provide the customer with an easy way of changing the IRQ defined in sdevice(F).