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[BOS.git] / doc / services.txt

SYSTEM SERVICES LAYOUT
======================

All  OS functionality  can be reached from one  or  several
interfaces/services.

When calling the  system interrupt  0x32,  you request a service
number and function in AX register with AL & AH. Making 256 the max
number of interfaces and available service-functions.

Services numbered 0x0F and below are system reserved and will not be
assigned automatically when requesting to add a new service. They can
still be replaced by implicitly requesting that service number instead
of getting a free one assigned.

This will allow for great OS modularity when each interface/service-
group can be replaced or upgraded by any user software or driver.

Most service groups or interfaces can be extended with drivers for
the type of device(s) that it handles, or the full service/interface
can be replaced for more fundamental changes to the design. For
example the 'process' and 'memory' interfaces can be replaced to
allow more advanced functionality like multitasking and paging.

The OS will be unable to function at all without the basic service
0x00 that performs the most crucial tasks, and without the STDIO and
VFS interfaces it will be severly crippled, left with no means of
communication, except perhaps a beep or two from the PC-speaker.

Below is a more visual representation of the main OS services
that will likely be included in the kernel. And a draft of what
functions each could or would include.  Some functions also have
a breif example of parameters required.

Possible funture service groups or interfaces that could be system
default include: 
- network functionality
- general PCI devices
- special one for all things USB?
- GUI specific functions
- printing services
- running stuff in 16 and 64 bit, with extra DOS emulation
  and/or other services




services.asm  (main service 0x00)
--------------------------------------
  always present in BOS, kernel 
--------------------------------------
   - add service
        signature       dd  'VFS ', 'IO  ', 'SND ', 'PCI '
        version         db  1
        requested_no    db  23    ; 0xFF or 0x00 to get assigned
        service_struct  dd  0     ; memory address of service calltable
   - get servide
        AL = number
        returns all info above if service found
   - remove service
        AL = number
        removes / unloads a service/interface
   - get free number
        AL = free service number  ; always above 0x0F (below reserved)
   - get BOS version (and other misc. kernel functions below)
   - get/set interrupts
   - execute kernel monitor command/script
   - get time/date
   - GDT function, create new segments 'n shit
   - pc-speaker beep if not even stdio is found
   - CMOS / PIC functions


stdio.asm (service number 0x01)
--------------------------------------
  needs to init itself as a service,
  requesting servicenumber 1.
  internal struct with info on
  default in and out devices.
--------------------------------------
   - add device
        type            db  1        ; 0 = output, 1 = input
        signature       dd  'COM ', 'VGA ', 'VESA', 'FILE', 'NET ', 'USB ', 'KEYB', 'MICE'
        version         db  1
        device_struct   dd  0     ; address of calltable
   - get device
        AL = assigned device type ID / 0 for default?
        returns all info above
   - remove device
        AL = assigned device type ID
        removes device
   - set default
        AL = assigned device type ID
        AH = 1 for in, 0 for out
   - getc
        get a char from stdin or specified device
   - putc
        put a char to stdout or specified device

   .... other default stubs needed for STDIO ....


vfs.asm (service number 0x02)
--------------------------------------
  needs to init itself as a service,
  requesting servicenumber 2.
  internal struct with info on
  devices and filesystems.
  add simple 'FILE' STDIO interface?
--------------------------------------
   - add device
   - remove device
   - get devices (list or number specified)
   - read sector
   - write sector
   - seek
   - more device specific stubs?
   ...
   - add fs
   - remove fs
   - parse path
   - load file
   - write file
   - seek file
   - close file
   - mount device (with auto detect fs option)
   - format fs (take device argument)
   - more fs specific stubs?


proccess.asm (service number 0x03)
--------------------------------------
  needs to init itself as a service,
  requesting servicenumber 3.
  possible to extend/replace for
  multitasking.
--------------------------------------
   - Load process
       needs VFS info to load file
   - Exit process
   - Terminate and Stay Resident
   - Add exec. driver
       interface to load driver/extensions for
       more executable formats, possibly other
       execution modes: realmode, longmode
   - Remove driver
   - run 16/64 bit code - seperate services for this? (int21h included?)


memory.asm (service number 0x04)
--------------------------------------
  needs to init itself as a service,
  requesting servicenumber 4.
--------------------------------------
   - lowalloc ? (for low mem, DMA & 16bit code)
   - alloc
   - realloc
   - free
   - DMA functions here? Possibly most related to mem?