Source Code 1992 March

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Text File | 1990-12-28 | 19KB | 429 lines

README file for the FAS Final Async Solution driver --------------------------------------------------- What is this package: This is an async driver for 386 based unix systems that adds several features that are not supported by vendors drivers. It supports 1. the NS16550A and i82510 UART chips in full FIFO mode. 2. modem sharing for input and output. 3. shared interrupts. 4. hardware flow control. 5. VP/ix, the ISC DOS emulator. FAS was successfully tested under the following operating systems: Microport UNIX SYSV 3.0 ISC 386/ix 2.0.2 & 2.2 ESIX Rev. C & D SCO UNIX 386 SCO XENIX 386 2.3.2 This driver should work with most of the UNIX SYS V/386 3.X ports currently available. You can have both this and the original vendor driver in the same kernel (if you really like to, but I wouldn't know why). Each driver controls its own separate set of serial ports. The only restriction here is that any int vector must not be used by more than one of the drivers. The kernel config program will complain otherwise. ------------------------------------------------------------------------ How it works: DIALIN/DIALOUT ON THE SAME PORT ------------------------------- This driver supports shared line usage by having two logical devices sharing one physical line. Each logical device has its own name. For example for the first line the names are ttyF00 (minor device 0) and ttyFM00 (minor device 192). The ttyF00 is used for cu, kermit, and other programs that want to dial out. It ignores the modem signals and just goes to it. The ttyFM00 line is strictly for getty. When getty calls open on ttyFM00 the driver hangs the open until the modem asserts the carrier detect signal and then lets the open complete. If cu opens ttyF00 while getty is waiting for the open to complete the device is given to cu and the getty open must wait for cu to finish and then will again wait for the carrier. If cu tries to open the ttyF00 line while getty has ttyFM00 open cu will get an error. If getty tries to open ttyFM00 while cu has ttyF00 open the getty open will just hang and wait for cu to close the line and then wait for the carrier. To put it simply you should put up a getty on ttyFM00 with a -t 60 and use ttyF00 for cu and uucico. In the example above ttyF00 had a minor device number of 0 and ttyFM00 one of 192. But there are several other possible minor device numbers for each port. The higher bits of the minor device number control the operating mode of the device. The port can't be opened by two or more different minor devices at the same time. - Minor devices that *don't* block on open if no carrier is present: Bitmap: 0 m m h x x x x `m m' are the mode bits as follows: 0 0 The carrier signal is totally ignored. With carrier high->low *no* SIGHUP signal is generated. 0 1 After an initial open, the carrier signal is ignored. Although, carrier high->low generates a SIGHUP signal. From thereon the device is carrier controlled until the last process has closed the device. An ioctl call with a TCSETA* command resets the device to ignore carrier again until the next carrier high->low. 1 0 The device is carrier controlled. Additionally, if on open the carrier signal is low, a SIGHUP signal is sent immediately. 1 1 The device behaves the same as with mode `0 1'. Additionally, if on open the carrier signal is low, a SIGHUP signal is sent immediately. - Minor devices that *do* block on open if no carrier is present: Bitmap: 1 m m h x x x x `m m' are the mode bits as follows: 0 0 The device is carrier controlled. 0 1 The device is carrier controlled. An unblock signal wakes up the waiting open and I/O is possible regardless of carrier until a carrier high->low. Thereafter the device is again fully carrier controlled. 1 0 Same as mode `0 0', but a parallel non-blocking open is possible while waiting for carrier. 1 1 Same as mode `0 1', but a parallel non-blocking open is possible while waiting for carrier. - Description of the remaining bits of the bitmap: `h' If set to `1', the device has hardware handshake. Refer to the `space.c' file to determine which port signals are actually used for that purpose. If set to `0' hardware handshake is depending on the termio(7) CTSFLOW and RTSFLOW flags (if they are available). `x x x x' This is the physical port number. This driver supports up to 16 ports. If you need more, you should use an intelligent serial card because more than 16 devices will eat up to much CPU time with this dumb-port approach. - Note: If a device is carrier controlled, this implies the generation of a SIGHUP signal with every carrier high->low. This is of course only true if the CLOCAL flag is *not* set. On my own system I prefer a minor device number of `0011xxxx' (48 + device #) for the non-blocking tty node and `1101xxxx' (208 + device #) for the blocking tty node. This gives me the SIGHUP signal on carrier loss and hardware flow control with both logical devices. Dialout while a dialin open is waiting for the carrier is also possible with this setup. WHICH SERIAL CARDS ARE SUPPORTED ? ---------------------------------- The driver supports and has been tested on many async cards and mux boards. It supports most combinations of shared interrupts. The current driver supports NS16450, NS16550A, um82450 and i82510. 8250 chips are not supported due to various bugs and speed problems in these parts. They have no place in any 386 or other high performance system. Replace them with one of the supported chips. They are pin-to-pin compatible. Take a look at the various samples of space-xxxx for details of how to set up for various devices. At boot time you will see a status message on the screen with symbols that show the init state of each port. The symbols are as follows: - not defined in the fas_port array ? can't initialize port 1-6 error during test phase indicated by number * port is initialized f port is initialized and has FIFOs (i82510) F port is initialized and has FIFOs (NS16550) This is convenient to check whether you have entered the proper port base addresses in `space.c'. WHICH CARD WILL SUPPORT SHARED INTERRUPTS ? ------------------------------------------- Many multi-port cards have jumpers or dip switches that let you assign more than one port to the same interrupt (IRQ) line. This alone is _no_ guaranty that they really support shared interrupts! These cards may be designed for the DOS world where you may want two or more serial ports but don't need to run them concurrently, that is, no more than one of those ports assigned to the same IRQ line is allowed to be in use at a time. For DOS this is sufficient as DOS is no multitasking operating system. For UNIX this won't work because in the worst case all serial ports may be in use at the same time. The basic problem is that the PC (and AT) I/O bus can't handle shared interrupts itself. This is due to a brain-dead hardware design. Therefor there must be some special logic on the serial card to provide shared interrupts. And those cards are quite rare (and usually more expensive). Therefor, you have the choice to give every port on the card its own IRQ line or to buy a multi-port card that really has shared interrupts. But in the latter case you better ask your vendor twice to make shure that it has this functionality because from the card's manuals it often isn't obvious which type of card it is. One well-known shared interrupts card is the AST 4-port card. There are many compatible clones available that are usually much cheaper than the original. You can even buy AST compatible 8-port cards where two AST 4-port blocks are on the same board. A WORD ABOUT CHARACTER LOSSES ----------------------------- If you've experienced character losses with your vendor async driver at high baud rates you shouldn't blame the vendor for that. The real reason for this problem lies in the ancient port devices used in most 386 systems: The 8250 (not supported by FAS) and the NS16450. They have only one receiver character buffer. This implies that the operating system must read a character from this buffer before the next one arrives from the port's shift register. For the old IBM PC with DOS this was sufficient. But for UNIX and with baud rates up to 38400 this is simply a joke. UNIX is not a real-time operating system. That means that it's kernel isn't optimized for fast interrupt responses. With the proper hardware this is no problem. But because the vendors have to adapt UNIX to the standard hardware found in 386 systems they also have to cope with the NS16450 ports which are in there simply to be compatible with IBM PCs, XTs and ATs. It is impossible to make it work at high baud rates without a major redesign of the AT&T supplied UNIX kernel. But then it wouldn't be UNIX SYSV any more. Luckily, there is a pin-to-pin replacement available from National Semiconductors: The NS16550A. This device has separate 16 character FIFOs for the receiver and the transmitter. With these FIFOs the interrupt latency of the kernel can be quiet high without losing any characters. Additionally, because with most interrupts many characters are processed at once the system is loaded much less. As you see, the necessary hardware is available. Therefor, if you have to blame the UNIX vendor then blame him for not telling you that you should buy some NS16550A and/or for not supplying you with a serial driver that supports these port devices. But as you have the FAS driver now and if you use the NS16550A devices you shouldn't have this kind of trouble any more. This is the philosophy behind the driver's name `Final Async Solution'. Enjoy! PS: If for some reason you can't get the NS16550A chips you could use the i82510 chips from Intel. Although they are much less efficient they are still better than the NS16450. HARDWARE FLOW CONTROL --------------------- FAS will support hardware flow control, also known as RTS/CTS full duplex flow control, by default. This is a method to control character flow in both input and output directions. You can enable hardware flow control via the minor device number of the port or with the termio(7) RTSFLOW/CTSFLOW flags (if your UNIX has them). The RS232C RTS line controls the input direction and the CTS line is responsible for the output direction. As long as the FAS input buffer hasn't reached a certain threshold the RTS line is set high to signal the connected device that it may send characters. If the input buffer level rises beyond this threshold RTS will go low and the device is supposed to stop sending characters. As soon as there is sufficient space in the input buffer RTS will go high again and the character flow may continue. The CTS line works the other way round. If the connected device sets CTS to high the FAS character output is enabled. If CTS is low, the output is stopped. There is a special feature for the CTS part of the handshake. CTS is only looked at if the DSR line is high. If DSR is low or not connected hardware output handshake is disabled, that is, FAS sends characters regardless of the state of CTS. This has two advantages. At first, if you switch off a serial device connected to an FAS port with hardware flow control CTS will go low and therefor the output gets blocked. If at this time there are still characters in the output buffer the last process closing this port can't terminate until the buffer has drained. You can't even kill the process in this state. It will become one of those infamous immortal processes. But as DSR will also go low if you switch off the device this blocking of the output will be prevented. In short: Hardware output handshake is only used if the connected device sets DSR high, that is, the device is switched on and is ready. So make sure that you keep this in mind when you make serial cables and when you configure your serial devices. DSR must be on if you want CTS handshake. The other advantage of this CTS/DSR mechanismn is that you can still connect dumb serial devices to an FAS hardware handshake port using a minimal 3-wire cable. As an unconnected DSR line is automatically low hardware output handshake is disabled, which is just what you wanted in this case. VP/ix SUPPORT ------------- FAS allows DOS programs running under VP/ix to access serial ports. You simply need to modify your personal VP/ix configuration file (`vpix.cnf') to tell the DOS emulator which FAS devices to use for COM1 (or COM1MOUSE) and COM2. Note that VP/ix opens these devices at startup time, so you better make sure that the desired devices aren't used by other processes when you start VP/ix as VP/ix wants to use them exclusively. There are some special features with the handling of the RTS and DTR lines you should know about. If your DOS program asserts the DTR line this will actually cause action on the modem enable line you configured in `space.c'. Likewise, RTS asserts the input hardware handshake line configured in `space.c'. If the used FAS device has hardware handshake enabled, asserting RTS from DOS actually stops the character flow from FAS to VP/ix. This prevents input buffers of interrupt driven DOS programs from overflowing. FAS, on the other hand, uses its hardware handshake to prevent an overflow of its own input buffer. Therefor you can use DOS telecommunication programs even at high baud rates without losing characters, provided your DOS programs are configured to use RTS/CTS flow control. All this virtual handling has the advantage that the DOS program doesn't need to know certain details about your actual port setup. Reading the modem status register, on the other hand, doesn't cause any translation of the register value. To enable VP/ix support, you have to uncomment the `HAVE_VPIX' define in `fas.h'. ------------------------------------------------------------------------ What's in this package: README This file. INSTALLATION A description about how to install the driver on your system. PATCHLEVEL Just a reference file for future updates. RELEASENOTES Notes about the present FAS releases. fas.h The header file for the driver. fas.c The driver itself. space-xxxxx These are samples of what `space.c' must look like. You can either copy one of these to `space.c' or use it as a template to create your own `space.c'. space-c1-2 For com1 and com2. space-c1-3 For com1, com2 and com3. space-ast4 For the AST 4-port card. config-xxxxx This is for uPort SYS V/386 only. Kernel configuaration file. You should pick the one that matches your configuration and copy it to `config'. config-c1-2 For com1 and com2. config-c1-3 For com1, com2 and com3. config-ast4 For the AST 4-port card. s_fas-xxxxx This is for ISC 386/ix, ESIX and SCO UNIX 386. Kernel configuration file. You should pick the one that matches your configuration and copy it to `s_fas'. s_fas-c1-2 For com1 and com2. s_fas-c1-3 For com1, com2 and com3. s_fas-ast4 For the AST 4-port card. n_fas-xxxxx This is for ISC 386/ix, ESIX and SCO UNIX 386. Tty device nodes file. You should pick the one that matches your configuration and copy it to `n_fas'. n_fas-c1-2 For com1 and com2. n_fas-c1-3 For com1, com2 and com3. n_fas-ast4 For the AST 4-port card. i_fas-xxxxx This is for ISC 386/ix, ESIX and SCO UNIX 386. Inittab getty lines file. You should pick the one that matches your configuration and copy it to `i_fas'. i_fas-c1-2 For com1 and com2. i_fas-c1-3 For com1, com2 and com3. i_fas-ast4 For the AST 4-port card. makefile.uPort A makefile for uPort SYS V/386 systems. This is generic and should work for all configurations of lines and interrupts. makefile.ISC A makefile for ISC 386/ix systems. This is generic and should work for all configurations of lines and interrupts. makefile.ESIX A makefile for ESIX systems. This is generic and should work for all configurations of lines and interrupts. makefile.SCO A makefile for SCO UNIX 386 systems. This is generic and should work for all configurations of lines and interrupts. makefile.XENIX A makefile for SCO Xenix 386 systems. This is generic and should work for all configurations of lines and interrupts. ------------------------------------------------------------------------ What you will need to use this package: You will need one of the above mentioned UNIX systems with the kernel link kit and the software development package. ------------------------------------------------------------------------ Originally written by Jim Murray encore!cloud9!jjmhome!jjm 2 Mohawk Circle harvard!m2c!jjmhome!jjm Westboro Mass 01581 jjm%jjmhome@m2c.m2c.org USA voice (508) 366-2813 Current author: Uwe Doering Domain : gemini@geminix.in-berlin.de Billstedter Pfad 17 b Bangpath : ...!unido!fub!tmpmbx!geminix!gemini 1000 Berlin 20 Germany