DGB(4)

NAME
dgb - DigiBoard intelligent serial cards driver

SYNOPSIS
options "NDGBPORTS=8"
device dgb0 at isa? tty port 0x220 iomem 0xfc0000 iosiz ? flags 0x0 All values are just examples.

The NDGBPORTS option defines the total number of ports on all cards installed in the system. When not defined the number is computed:
default NDGBPORTS = number_of_described_DigiBoard_cards * 16 If it is less than the actual number of ports the system will be able to use only the first NDGBPORTS ports. If it is greater then all ports will be usable but some memory will be wasted.

Meaning of flags:
0x0001 use alternate pinout (exchange DCD and DSR lines)
0x0002 don't use 8K window mode of PC/Xe

Device numbering:
0bCCmmmmmmmmOLIPPPPP
CCard number
mmmmmmmmajor number
callOut
Lock
Initial
PPPPPort number

DESCRIPTION
The dgb driver provides support for DigiBoard PC/Xe and PC/Xi series intelligent serial multiport cards with asynchronous interfaces based on the EIA RS-232C (CCITT V.24) standard.

Input and output for each line may set to one of following baud rates; 50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, or for newer versions of cards 115200.

The driver doesn't use any interrupts, it is ``polling-based''. This means that it uses clock interrupts instead of interrupts generated by DigiBoard cards and checks the state of cards 25 times per second. This is practical because the DigiBoard cards have large input and output buffers (more than 1Kbyte per port) and hardware that allows efficiently finding the port that needs attention. The only problem seen with this policy is slower SLIP and PPP response.

Each line in the kernel configuration file describes one card, not one port as in the sio driver.

The flags keyword may be used on each device dgb line in the kernel configuration file to change the pinout of the interface or to use new PC/Xe cards which can work with an 8K memory window in compatibility mode (with a 64K memory window). Note that using 8K memory window doesn't mean shorter input/output buffers, it means only that all buffers will be mapped to the same memory address and switched as needed.

The port value must be the same as the port set on the card by jumpers. For PC/Xi cards the same rule is applicable to the iomem value. It must be the same as the memory address set on the card by jumpers. For PC/Xe cards there is no need to use jumpers for this purpose. In fact there are no jumpers to do it. Just write the address you want as the iomem value in kernel config file and the card will be programmed to use this address.

The same range of memory addresses may be used for all the DigiBoards installed (but not for any other card or real memory). DigiBoards with a large amount of memory (256K or 512K and perhaps even 128K) must be mapped to memory addresses outside of the first megabyte. If the computer has more than 15 megabytes of memory then there is no free address space outside of the first megabyte where such DigiBoards can be mapped. In this case you may need to reduce the amount of memory in the computer. But many machines provide a better solution. They have the ability to ``turn off'' the memory in the 16th megabyte (addresses 0xF00000 - 0xFFFFFF) using the BIOS setup. Then the DigiBoard's address space can be set to this ``hole''.

Serial ports controlled by the dgb driver can be used for both `callin' and `callout'. For each port there is a callin device and a callout device. The minor number of the callout device is 128 higher than that of the corresponding callin port. The callin device is general purpose. Processes opening it normally wait for carrier and for the callout device to become inactive. The callout device is used to steal the port from processes waiting for carrier on the callin device. Processes opening it do not wait for carrier and put any processes waiting for carrier on the callin device into a deeper sleep so that they do not conflict with the callout session. The callout device is abused for handling programs that are supposed to work on general ports and need to open the port without waiting but are too stupid to do so.

The dgb driver also supports an initial-state and a lock-state control device for each of the callin and the callout "data" devices. The minor number of the initial-state device is 32 higher than that of the corresponding data device. The minor number of the lock-state device is 64 higher than that of the corresponding data device. The termios settings of a data device are copied from those of the corresponding initial-state device on first opens and are not inherited from previous opens. Use stty(1) in the normal way on the initial-state devices to program initial termios states suitable for your setup.

The lock termios state acts as flags to disable changing the termios state. E.g., to lock a flag variable such as CRTSCTS, use stty crtscts on the lock-state device. Speeds and special characters may be locked by setting the corresponding value in the lock-state device to any nonzero value.

Correct programs talking to correctly wired external devices work with almost arbitrary initial states and no locking, but other setups may benefit from changing some of the default initial state and locking the state. In particular, the initial states for non (POSIX) standard flags should be set to suit the devices attached and may need to be locked to prevent buggy programs from changing them. E.g., CRTSCTS should be locked on for devices that support RTS/CTS handshaking at all times and off for devices that don't support it at all. CLOCAL should be locked on for devices that don't support carrier. HUPCL may be locked off if you don't want to hang up for some reason. In general, very bad things happen if something is locked to the wrong state, and things should not be locked for devices that support more than one setting. The CLOCAL flag on callin ports should be locked off for logins to avoid certain security holes, but this needs to be done by getty if the callin port is used for anything else.

FILES
/dev/ttyD??
    for callin ports
/dev/ttyiD??
/dev/ttylD??
    corresponding callin initial-state and lock-state devices

/dev/cuaD??
    for callout ports
/dev/cuaiD??
/dev/cualD??
    corresponding callout initial-state and lock-state devices

/etc/rc.serial
    examples of setting the initial-state and lock-state devices

The first question mark in these device names means the number of the card from the set [0-9] and the second question mark means the number of the port on the card from the set [0-9a-v].

DIAGNOSTICS
You may enable extended diagnostics by defining DEBUG at the start of the source file dgb.c.

dgbX: warning: address N truncated to M The memory address for the PC/Xe's 8K window is misaligned (it should be on an 8K boundary) or outside of the first megabyte.

dgbX: 1st reset failed Problems with accessing I/O port of the card, probably the wrong port value is specified in the kernel config file.

dgbX: 2nd reset failed Problems with hardware.

dgbX: N[st,nd,rd,th] memory test failed Problems with accessing the memory of the card, probably the wrong iomem value is specified in the kernel config file.

dgbX: BIOS start failed Problems with starting the on-board BIOS. Probably the memory addresses of the DigiBoard overlap with some other device or with RAM.

dgbX: BIOS download failed Problems with the on-board BIOS. Probably the memory addresses of the DigiBoard overlap with some other device or with RAM.

dgbX: FEP code download failed Problems with downloading of the Front-End Processor's micro-OS. Probably the memory addresses of the DigiBoard overlap with some other device or with RAM.

dgbX: FEP/OS start failed Problems with starting of the Front-End Processor's micro-OS. Probably the memory addresses of the DigiBoard overlap with some other device or with RAM.

dgbX: too many ports This DigiBoard reports that it has more than 32 ports. Perhaps a hardware problem or the memory addresses of the DigiBoard overlap with some other device or with RAM.

dgbX: only N ports are usable The NDGBPORTS parameter is too small and there is only enough space allocated for N ports on this card.

dgbX: port Y is broken The on-board diagnostic has reported that the specified port has hardware problems.

dgbX: polling of disabled board stopped Internal problems in the polling logic of driver.

dgbX: event queue's head or tail is wrong! Internal problems in the driver or hardware.

dgbX: port Y: got event on nonexisting port Some status changed on a port that is physically present but is unusable due to misconfiguration.

dgbX: port Y: event N mstat M lstat K The driver got a strange event from card. Probably this means that you have a newer card with an extended list of events or some other hardware problem.

dgbX: port Y: overrun Input buffer has filled up. Problems in polling logic of driver.

dgbX: port Y: FEP command on disabled port Internal problems in driver.

dgbX: port Y: timeout on FEP command Problems in hardware.

SEE ALSO
tty(4), termios(4), comcontrol(8), MAKEDEV(8), stty(1).

HISTORY
The dgb driver is derived from the sio driver and the DigiBoard driver from Linux and is

BUGS
The implementation of sending BREAK is broken. BREAK of fixed length of 1/4 s is sent anyway.

There was a bug in implementation of select(2). It is fixed now but not widely tested yet.

There is no ditty command. Most of its functions (alternate pinout, speed up to 115200 baud, etc.) are implemented in the driver itself. Some other functions are missing.