Subsystem Stubs

Document Revision: 26h1.1

The following subsystems have source directories and header files but are not yet implemented.

IRQ (arch/s390x/irq/)

Handles I/O interrupts from the channel subsystem. The I/O new PSW at lowcore 0x1E0 must point to the I/O interrupt handler. The handler calls TSCH to read the IRB and dispatches to the appropriate device driver.

Status: Stub — new PSW installed as disabled-wait.

Time (arch/s390x/time/)

Provides kernel timekeeping using the TOD (Time-of-Day) clock. The TOD clock is a 64-bit counter incremented at 4096 Hz. The boot timestamp is available in proto->tod_boot. The clock comparator interrupt (external interrupt subclass) drives the scheduler tick once the IRQ subsystem is active.

Status: Stub.