Simtel MSDOS 1992 June/SIMTEL_0692.cdr/msdos/screen/vdriver.arc/DRIVER.DOC

Text File | 1986-09-21 | 4.8 KB | 175 lines

                 Installable Device Drivers in C


This document is intended to describe a method for using Lattice
C (small model) to develop Installable Device Drivers for MS-DOS.
Additionally, a number of C functions (provided in library
format) are defined.

Installable Device Drivers are created by first writing the
functions to be supported, then linking these functions with the
Driver Header.  A prototype header file is provided in the file
HDR.ASM.  Note that two data items (the Attribute and Name/unit
fields) must be filled in with information specific to your
driver before this file will assemble properly.

The driver header file assumes the existence of the following
functions (stubs are provided in the DRIVER.LIB library file),
which perform the various operations described in the Installable
Device Drivers chapter of the DOS Reference Manual:

          Init()
          MediaCheck()
          BuildBPB()
          IoCtlIn()
          Input()
          ndInput()
          InputStatus()
          InputFlush()
          Output()
          OutVerify()
          OutStatus()
          OutFlush()
          IoCtlOut()
          DevOpen()
          DevClose()
          RemMedia()

A sample character device driver is included in this package,
which allows for a device named "MON".  Outputting to this device
will cause characters to appear on the IBMPC monochrome screen.
Study of the file MONO.C should reveal the details of this
implementation.

     Questions or comments on this package may be directed to:

                          Frank Whaley
                       7211 Camino Colegio
                     Rohnert Park, CA  94928

Through the balance of this document, the pseudo-type "Addr" is
used to describe a long integer value (32-bits) which is used to
describe a memory address.  Note that the Segment:Offset
addressing method used in the 8086 family of processors causes
this data type to be incompatible with true long integers.  The
following definition is assumed:

                      typedef   long Addr;


Addr EndAddr();

     EndAddr() returns the driver's ending address, as required
     by the Init function call.


Addr Dword(ptr)
         char    *ptr;

     Dword() converts a 16-bit pointer (into the driver's data
     segment) to a 32-bit pointer.


int CopyB(from, to, len)
    Addr    from,
        to;
    int    len;

     CopyB() copies a section of memory "len" bytes in length
     from the area whose address is "from" to the area whose
     address is "to".  Note that this code assumes that the
     memory sections do not overlap and that a forward copy is
     correct.  This function returns the number of bytes copied.


int CopyW(from, to, len)
    Addr    from,
        to;
    int    len;

     CopyW() copies a section of memory "len" words in length
     from the area whose address is "from" to the area whose
     address is "to".  Note that this code assumes that the
     memory sections do not overlap and that a forward copy is
     correct.  This function returns the number of words copied.

char InB(port)
    int    port;

     InB() inputs and returns a byte from the hardware port
     described by "port".


int InW(port)
    int    port;

     InW() inputs and returns a word from the hardware port
     described by "port".


char OutB(byte, port)
    char    byte;
    int    port;

     OutB() outputs the byte "byte" to the hardware port
     described by "port".  This function returns the output byte.


int OutW(word, port)
    int    word,
        port;

     OutW() outputs the word "word" to the hardware port
     described by "port".  This function returns the output word.


char PeekB(addr)
    Addr    addr;

     PeekB() returns the byte value found at the absolute address
     given by "addr".


int PeekW(addr)
    Addr    addr;

     PeekW() returns the word value found at the absolute address
     given by "addr".

char PokeB(val, addr)
    char    val;
    Addr    addr;

     PokeB() stores the value "val" into the absolute byte
     address given by "addr".  This function returns "val".


int PokeW(val, addr)
    int    val;
    Addr    addr;

     PokeW() stores the value "val" into the absolute word
     address given by "addr".  This function returns "val".


int SetB(start, len, byte)
    Addr    start;
    int    len;
    char    byte;

     SetB() initializes a section of memory "len" bytes in
     length, beginning with the address given by "start", to the
     value "byte".  This function returns the number of bytes
     set.


int SetW(start, len, word)
    Addr    start;
    int    len,
             word;

     SetW() initializes a section of memory "len" words in
     length, beginning with the address given by "start", to the
     value "word".  This function returns the number of words
     set.