System information

5 Device Emulation

One of the most important feature of a remote management card is the interaction with

the host. Keyboard and mouse interactions from the commanding computer have to be

transmitted to the remote managed host. The CHARM card has USB interfaces to facilitate

these devices. Additionally, the CHARM card implements also a USB mass storage device.

For this reason, the card can provide a boot device to the host computer. The USB mass

storage implementation is separate in two parts: one for the high level USB protocol and

one for the SCSI

commands inside the USB packets. By the reason of this approach, the

software, processing the SCSI commands can also used for the device emulation via PCI.

The next development step is the reduction of the USB interface. With the aid of the PCI

interface, the CHARM could implement a BEV

or BCV

device. BCV or BEV devices are

IPL

devices that has the ability to load and execute an OS.

The host interaction can be accomplished by the PCI interface, too. At boot time, the

CHARM card can use the BIOS keyboard buﬀer to emulate keystrokes. Additionally, the

CHARM card can also access the PS/2 keyboard controller on the mainboard. The ﬁrst

sections of this chapter discuss device emulation via USB. After a brief overview of the

USB protocol, the USB interface of the CHARM will be explained. Section 5.1.3 and 5.1.4

illustrate the USB device emulation done in the CHARM more in detail. At the end of the

chapter, the keyboard interaction using the PCI interface is presented.

5.1 USB Device Emulation

The onboard USB controller undertakes the low level USB protocol. It interfaces with the

onboard USB plugs and the Excalibur device. Section 5.1.2 discusses the interface and

feature of the USB chip. Basically, only one of the four existing USB connectors on the

CHARM is used. This is realized by the implementation of a USB composite device. Such

devices provide several independent functions at a single USB connection. The CHARM

card provides a keyboard, a mouse and a mass storage function. The usage of USB has

the advantage to emulated a variety of device. Hence, the CHARM function can easily

expand with new features. For example, the CHARM can provide a video device at its

USB interface on the card bracket. The host screen can be made available to this video

device and emulates a kind of VGA plug on a graphic card. Thereby, the host can be

commanded even if the network connection is down. But in this case, two USB connection

are used: one for the host and one for the inspecting computer obtaining the host screen

Small Computer System Interface

A Bootstrap Entry Vector is a pointer that points to code inside an option ROM [67].

A Boot Connection Vector is a pointer that points to code inside the option ROM that will perform

device initialization [67].

Initial Program Load