The UIM calls the device lookup routine to perform the following functions:

• Return all the devices grouped together by means of the PCU number (Applicable to graphic controllers only)
• Return all the devices that are attached to the same control unit
• Return the control unit information (type and model) of the control unit identified by its control unit number
• Return the device record for a given device number

The device information is returned in the format of an IODV record — one after the other. The UIM must provide a pointer to the IODV and data area.

The device lookup routine returns data in an I/O device internal text record (IODV) format. The DEVL parameter list contains a pointer to an area large enough to hold an IODV. The device lookup routine fills that area with device information in the IODV format.

To call the device lookup routine within a UIM, use a BALR instruction in 31-bit addressing mode. Use standard register save area conventions. The UCADEVP field in the UCA contains the address of the device lookup routine.

Device Lookup Routine Input Parameters

A UIM provides the input to the device lookup routine in the DEVL parameter list. The DEVL parameter list resides in the UIM and is mapped by CBDZDEVL.

Registers on Entry to the Device Lookup Routine

Register 0

Undefined

Register 1

Pointer to a two-word parameter list

• Word 1 - Address of the UCA
• Word 2 - Address of the DEVL parameter list

Register 2-12

Undefined

Register 13

Address of an 18-word save area

Register 14

Return address

Register 15

The device lookup routine entry point address

Registers on Exit from the Device Lookup Routine

Register 0-14

Restored

Register 15

Return code

Return Codes

RC 0

Device or control unit found.

RC 4

Device or control unit not found or no more devices or control units available matching the setup criteria

RC 8

Supplied data area too short (that means the storage area for the IODV record)

RC 12

Invalid function code passed