ChorusOS 5.0 Features and Architecture Overview

Hot Swap Sequences

The BSP hot swap feature of the ChorusOS operating system performs the following operations upon system start-up and the insertion or removal of a board.

Start up

When started, the PciSwap device driver looks up the device registry for the HSC device driver specified for its node. If found, the PciSwap driver opens the HSC device and installs its ENUM# handler. Without an ENUM# handler the PCI bus node will not support hot swap. The PCI bus driver init-method looks up the device registry and searches for the instance of the PciSwap driver specified for its device node. If found, the PCI bus driver opens the connection to this instance and installs its handlers for insertion and removal events. The PCI bus node now has hot swap capabilities.

Insertion of a Board

On insertion of a board, the ENUM# signal is detected and neutralized by the HSC device driver. This event is passed to the PciSwap driver, which detects the slot into which the board is inserted. The parent PCI bus driver is notified for each insertion. The PCI bus driver or PciSwap (or both) invokes the PCI enumerator. New device nodes are created or static nodes are activated. The device-specific driver establishes the connection to the PCI bus. The PCI bus driver invokes a lock method for each activated device node in the PciSwap driver. The slot is declared BUSY.

Removal of a Board

The ENUM# signal is detected by the HSC device driver. This event is passed to the PciSwap driver, which detects which slot to remove. The parent PCI bus driver is notified for each removal. The PCI bus driver sends the device shutdown event. The PCI device closes its connection to the PCI bus. The PCI bus driver or PciSwap (or both) invokes the PCI enumerator. The dynamic (enumerated) device nodes are deleted or static nodes are deactivated. When the last connection to the PCI bus driver for the slot is closed, the PCI bus driver invokes the method of the PciSwap driver. The slot is declared FREE and can be removed.

BSP Hot Swap API

The BSP hot swap feature API is given in the table below:

Function	Description
`open()`	Establish a connection between PCI bus and the Hot Swap Controller device.
`lock()`	Called before device initialization, to show that the PCI slot is busy.
`unlock()`	Called after device shut down, to show that the PCI slot is free to extract.
`close()`	Close a connection between PCI bus and the Hot Swap Controller device.