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Inside Macintosh: Devices /

Chapter 1 - Device Manager / Device Manager Reference

Device Manager Functions / Opening and Closing Device Drivers

OpenSlot

You can use the OpenSlot function to open a device driver that serves a slot device.

pascal OSErr OpenSlot(ParmBlkPtr paramBlock, Boolean async); 

paramBlock

A pointer to a SlotDevParam or MultiDevParam structure of the ParamBlockRec union.

async

A Boolean value that indicates whether the request is asynchronous. You must set this field to false because device drivers cannot be opened asynchronously.

<--	ioResult	OSErr	The device driver's result code.
-->	ioNamePtr	StringPtr	A pointer to the driver name.
<--	ioRefNum	short	The driver reference number.
-->	ioPermssn	char	Read/write permission.

Additional fields for a single device

-->	ioMix	Ptr	Reserved for use by the driver open routine.
-->	ioFlags	short	Determines the number of additional fields.
-->	ioSlot	char	The slot number.
-->	ioId	char	The slot resource ID.

Additional fields for multiple devices

-->	ioMMix	Ptr	Reserved for use by the driver open routine.
-->	ioMFlags	short	The number of additional fields.
-->	ioSEBlkPtr	Ptr	A pointer to an external parameter block.

DESCRIPTION

The OpenSlot function is equivalent to the PBOpen function, except that it sets bit 9 of the trap word, which signals the _Open routine that the parameter block includes additional fields.

If the sResource serves a single device, you should clear all the bits of the ioFlags field and include the slot number and slot resource ID in the ioSlot and ioID fields.

If the sResource serves multiple devices, you should set the fMulti bit (bit 0) of the ioFlags field (clearing all other bits to 0), and specify, in the ioSEBlkPtr field, an external parameter block that is customized for the devices installed in the slot.

SPECIAL CONSIDERATIONS

The OpenSlot function may move memory; you should not call it at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for the OpenSlot function is _Open (0xA200). Bit 9 of the trap word is set to signal that the parameter block contains additional fields for slot devices.

You must set up register A0 with the address of the parameter block. When _Open returns, register D0 contains the result code. Register D0 is the only register affected by this function.

Registers on entry
A0	Address of the parameter block

Registers on exit
D0	Result code

RESULT CODES

noErr	0	No error
badUnitErr	-21	Driver reference number does not match unit table
unitEmptyErr	-22	Driver reference number specifies a nil handle in unit table
openErr	-23	Requested read/write permission does not match driver's open permission
dInstErr	-26	Driver resource not found

SEE ALSO

For information about the low-level function for opening other device drivers, see the description of the PBOpen function on page 1-61. For an example of opening a device driver, see Listing 1-1 on page 1-18. Refer to the chapter "Slot Manager" in this book for more information about slot device drivers.