Use this system macro to perform a software mount of a symbolic device
address (SDA) that is associated with an input/output (I/O)
device. This allows the SDA to be used by the TPF system to perform
I/O operations through common I/O (CIO).
Format
- label
- A symbolic name can be assigned to the macro statement.
- MDR
- The mount device request (MDR) block, which can be either:
- label
- A symbol can be assigned to an area of memory that contains an MDR as
defined by the DCTMDR DSECT.
- (reg)
- A register that contains the address of the MDR.
Entry Requirements
- The MDR parameter must be coded with the SDA address and parameters
required to do the mount.
- The overlay option may be specified to switch the SDA parameters by
setting the MDROVL bit in field MDRFG1 of the DCTMDR mount device request
block DSECT. The code overlays the old parameters with the new
parameters, except for the I/O interruption subclass, which cannot be
changed. With overlay the code does not replace individual parameters
but does a complete replace. Those parameters that are not to be
replaced must still be specified in the MDR.
- Note:
- If the SDA is not already mounted then the overlay option is ignored and the
mount is treated as a normal mount request.
- The caller may request that program-controlled interrupts (PCIs) for this
device are to be treated as normal interrupts by setting the MDRNOPCI bit in
field MDRFG1 of the DCTMDR mount device request block DSECT. This
causes PCIs that are received while PIO is active to be stacked and presented
after PIO completes, rather than presented immediately. This option may
be requested for devices that can receive PCIs but whose interrupt handlers
are not coded to handle interrupts presented during system error
processing.
- I/O interrupts must be masked before macro invocation.
Return Conditions
- Control is returned to the next sequential instruction (NSI).
- R15 will contain one of the following return codes:
- Return Code
- Meaning
- 0
- The SDA mount was successful.
- 4
- The SDA is in use.
- 8
- The SDA is not valid.
- R0-R14 are unchanged.
- If the mount is successful, the channel path identifier (CHPID) type and
the subchannel path-available mask are returned to you through the MDR
block.
Programming Considerations
- This macro can be run only on an I-stream having affinity with the
specified SDA.
- This macro can be run only to mount SDAs that are associated with I/O
devices.
Examples
None.