source: xtideuniversalbios/trunk/Assembly_Library/Src/Serial/SerialServerScan.asm@ 611

; Project name  :   Assembly Library
; Description   :   Serial Server Support, Scan for Server

;
; This functionality is broken out from SerialServer as it may only be needed during
; initialization to find a server, and then could be discarded, (for example the case
; of a TSR).

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;


%include "SerialServer.inc"

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; SerialServerScan_ScanForServer:
;   Parameters:
;       BH:     Drive Select byte for Drive and Head Select Register
;               0xAx: Scan for drive, low nibble indicates drive
;               0x0:  Scan for Server, independent of drives
;       DX:     Port and Baud to Scan for
;               0: Scan a known set of ports and bauds
;       ES:SI:  Ptr to buffer for return
;   Returns:
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BX, CX, DX, DI
;--------------------------------------------------------------------
SerialServerScan_ScanForServer:
    mov     cx, 1           ; one sector, not scanning (default)

    test    dx, dx
    jnz     SHORT SerialServerScan_CheckForServer_PortAndBaudInDX

    mov     di, .scanPortAddresses-1
    mov     ch, 1           ;  tell server that we are scanning

.nextPort:
    inc     di              ; load next port address
    mov     dh, 40h         ; Clear DH and make sure CF is set if error
    mov     dl, [cs:di]
    eSHL_IM dx, 2           ; shift from one byte to two
    jz      SHORT .error

;
; Test for COM port presence, write to and read from registers
;
    push    dx
    add     dl, Serial_UART_lineControl
    mov     al, 9Ah
    out     dx, al
    in      al, dx
    pop     dx
    cmp     al, 9Ah
    jne     SHORT .nextPort

    mov     al, 0Ch
    out     dx, al
    in      al, dx
    cmp     al, 0Ch
    jne     SHORT .nextPort

;
; Begin baud rate scan on this port...
;
; On a scan, we support 6 baud rates, starting here and going higher by a factor of two each step, with a
; small jump between 9600 and 38800.  These 6 were selected since we wanted to support 9600 baud and 115200,
; *on the server side* if the client side had a 4x clock multiplier, a 2x clock multiplier, or no clock multiplier.
;
; Starting with 30h, that means 30h (2400 baud), 18h (4800 baud), 0Ch (9600 baud), and
;                               04h (28800 baud), 02h (57600 baud), 01h (115200 baud)
;
; Note: hardware baud multipliers (2x, 4x, 8x) will impact the final baud rate and are not known at this level
;
    mov     dh, 30h * 2     ; multiply by 2 since we are about to divide by 2
    mov     dl, [cs:di]     ; restore single byte port address for scan

.nextBaud:
    shr     dh, 1
    jz      SHORT .nextPort
    cmp     dh, 6           ; skip from 6 to 4, to move from the top of the 9600 baud range
    jne     SHORT .testBaud ; to the bottom of the 115200 baud range
    mov     dh, 4

.testBaud:
    call    SerialServerScan_CheckForServer_PortAndBaudInDX
    jc      SHORT .nextBaud

.error:
    ret

.scanPortAddresses:
    db  SERIAL_COM7_IOADDRESS >> 2
    db  SERIAL_COM6_IOADDRESS >> 2
    db  SERIAL_COM5_IOADDRESS >> 2
    db  SERIAL_COM4_IOADDRESS >> 2
    db  SERIAL_COM3_IOADDRESS >> 2
    db  SERIAL_COM2_IOADDRESS >> 2
    db  SERIAL_COM1_IOADDRESS >> 2
    db  0


;--------------------------------------------------------------------
; SerialServer_CheckForServer_PortAndBaudInDX:
;   Parameters:
;       BH:     Drive Select byte for Drive and Head Select Register
;               0xAx: Scan for drive, low nibble indicates drive
;               0x0:  Scan for Server, independent of drives
;       DX:     Baud and Port
;       CH:     1: We are doing a scan for the serial server
;               0: We are working off a specific port given by the user
;       CL:     1, for one sector to read
;       ES:SI:  Ptr to buffer for return
;   Returns:
;       AH:     INT 13h Error Code
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BX
;--------------------------------------------------------------------
SerialServerScan_CheckForServer_PortAndBaudInDX:
    push    bp              ; setup fake SerialServer_Command
    push    dx              ; send port baud and rate, returned in inquire packet
                            ; (and possibly returned in the drive identification string)
    push    cx              ; send number of sectors, and if it is on a scan or not
    mov     bl, SerialServer_Command_Inquire        ; protocol command onto stack with bh
    push    bx

    mov     bp, sp
    call    SerialServer_SendReceive

    pop     bx
    pop     cx
    pop     dx
    pop     bp

    ret