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This page needs improvement, but for now it contains some useful info about using the GSP with Linux.

Using the GSP card with Linux

The Guardian Service Processor card (recently renamed to Management Processor) can be a little confusing at first. This document attempts to explain how to use it to best effect under Linux. There is extensive online help available to you via the `HE` command, but it doesn't explain how it integrates with Linux (only HP-UX and MPE/ix ;-).

There have been several versions of this card; some are integrated onto the motherboard but most are PCI cards. This doesn't mean you can use them in a different slot, or in a different machine from the one they came in -- there are hardware dependencies.

There are 4 physical connectors (ports) to the GSP. One is the LAN port, the other three are RS232 serial ports. If you attach the so-called W cable to the 25-way socket on the back of the machine, you get all three (labelled Console, Remote and UPS or AUX). If you connect a regular 25-to-9-pin cable or adapter to the port, you get the Console port, which is incredibly cool.

On the software side, there are either 4 or 5 UARTs, depending on which version of the GSP you have. They are: Console, UPS/AUX, Remote Session, Internal (not present on all cards) and Local Session. I do not discuss the Internal UART in this document as I don't know how to use it, and it's removed from later cards anyway. How the UARTs map to the ports is partially under the control of the GSP card.

The UPS/AUX UART is always connected to the UPS/AUX port. By default, all the other ports are connected to the Console UART. Sending a `^B` to this UART breaks you into the GSP card interface. The intent is that you connect a serial console to the Console port and a modem to the Remote port. If you connect to either of these ports, break into the GSP interface and use the `SE` (session) command, it will attempt to connect you to either the local or remote session (depending if you're connected to the console or remote port, respectively).

In order to make use of the session, you'll need to make sure there are gettys running on the appropriate serial ports. If you look at dmesg, you'll see something like:

ttyS00 at iomem 0xfffffffff8000000 (irq = 132) is a 16550A
ttyS01 at iomem 0xfffffffff8000008 (irq = 132) is a 16450
ttyS02 at iomem 0xfffffffff8000010 (irq = 132) is a 16550A
ttyS03 at iomem 0xfffffffff8000038 (irq = 132) is a 16550A

`ttyS0` is the mirrored console UART, `ttyS1` is the UPS/AUX UART, `ttyS2` is the remote session and `ttyS3` is the local session. So take a look in `/etc/inittab` and you'll see something like:

T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100

Just add a couple of lines below this, changing them appropriately:

T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100
T2:23:respawn:/sbin/getty -L ttyS2 9600 vt100
T3:23:respawn:/sbin/getty -L ttyS3 9600 vt100

Now restart init with `telinit q` and you'll be able to start sessions. To disconnect from the session, just log out. The GSP detects the line drop and puts you back into the mirrored console UART.

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