source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Device/Serial/SerialCommand.asm@ 283

; Project name  :   XTIDE Universal BIOS
; Description   :   Serial Device Command functions.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; SerialCommand_OutputWithParameters
;   Parameters:
;       BH:     Non-zero if 48-bit addressing used
;               (ignored at present as 48-bit addressing is not supported)
;       BL:     IDE Status Register bit to poll after command
;               (ignored at present, since there is no IDE status register to poll)
;       ES:SI:  Ptr to buffer (for data transfer commands)
;       DS:DI:  Ptr to DPT (in RAMVARS segment)
;       SS:BP:  Ptr to IDEREGS_AND_INTPACK
;   Returns:
;       AH:     INT 13h Error Code
;       CX:     Number of successfully transferred sectors (for transfer commands)
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BX, CX, DX, (ES:SI for data transfer commands)
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
SerialCommand_OutputWithParameters:

        mov     ah,SerialServer_Command_Read

        mov     al,[bp+IDEPACK.bCommand]

        cmp     al,20h          ; Read Sectors IDE command
        jz      .readOrWrite
        inc     ah              ; now SerialServer_Protocol_Write
        cmp     al,30h          ; Write Sectors IDE command
        jz      .readOrWrite

;  all other commands return success
;  including function 0ech which should return drive information, this is handled with the identify functions
;
        xor     ah,ah           ;  also clears carry
        ret

.readOrWrite:
        mov     [bp+IDEPACK.bFeatures],ah       ; store protocol command

        mov     dx, [di+DPT_SERIAL.wSerialPortAndBaud]

        jmp     SerialServer_SendReceive


;--------------------------------------------------------------------
; SerialCommand_IdentifyDeviceToBufferInESSIwithDriveSelectByteInBH
;   Parameters:
;       BH:     Drive Select byte for Drive and Head Select Register
;       DS:     Segment to RAMVARS
;       ES:SI:  Ptr to buffer to receive 512-byte IDE Information
;       CS:BP:  Ptr to IDEVARS
;   Returns:
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BL, CX, DX, SI, DI, ES
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
SerialCommand_IdentifyDeviceToBufferInESSIwithDriveSelectByteInBH:
;
; To improve boot time, we do our best to avoid looking for slave serial drives when we already know the results
; from the looking for a master.  This is particularly true when doing a COM port scan, as we will end up running
; through all the COM ports and baud rates a second time.
;
; But drive detection isn't the only case - we also need to get the right drive when called on int13h/25h.
;
; The decision tree:
;
;    Master:
;          wSerialPortAndBaud Non-Zero:           -> Continue with wSerialPortAndBaud (1)
;          wSerialPortAndBaud Zero:
;              previous serial drive not found:   -> Scan (2)
;              previous serial drive found:       -> Continue with previous serial drive info (3)
;
;    Slave:
;          wSerialPortAndBaud Non-Zero:
;              previous serial drive not found:   -> Error - Not Found (4)
;              previous serial drive found:       -> Continue with wSerialPackedAndBaud (5)
;          wSerialPortAndBaud Zero:
;              previous serial drive not found:   -> Error - Not Found (4)
;              previous serial drive found:       -> Continue with previous serial drive info (6)
;
; (1) This was a port/baud that was explicitly set with the configurator.  In the drive detection case, as this
;     is the Master, we are checking out a new controller, and so don't care if we already have a serial drive.
;     And as with the int13h/25h case, we just go off and get the needed information using the user's setting.
; (2) We are using the special .ideVarsSerialAuto structure.  During drive detection, we would only be here
;     if we hadn't already seen a serial drive (since we only scan if no explicit drives are set),
;     so we go off to scan.
; (3) We are using the special .ideVarsSerialAuto structure.  We won't get here during drive detection, but
;     we might get here on an int13h/25h call.  If we have scanned COM drives, they are the ONLY serial drives
;     in use, and so we use the values from the previously seen serial drive DPT.
; (4) No master has been found yet, therefore no slave should be found.  Avoiding the slave reduces boot time,
;     especially in the full COM port scan case.  Note that this is different from the hardware IDE, where we
;     will scan for a slave even if a master is not present.  Note that if ANY master had been previously found,
;     we will do the slave scan, which isn't harmful, it just wastes time.  But the most common case (by a wide
;     margin) will be just one serial controller.
; (5) A COM port scan for a master had been previously completed, and a drive was found.  In a multiple serial
;     controller scenario being called with int13h/25h, we need to use the value in bSerialPackedPortAndBaud
;     to make sure we get the proper drive.
; (6) A COM port scan for a master had been previously completed, and a drive was found.  We would only get here
;     if no serial drive was explicitly set by the user in the configurator or that drive had not been found.
;     Instead of performing the full COM port scan for the slave, use the port/baud value stored during the
;     master scan.
;
        mov     dx,[cs:bp+IDEVARS.wSerialPortAndBaud]
        xor     ax,ax
        
        push    si
        call    FindDPT_ToDSDIforSerialDevice
        pop     si
%ifdef MODULE_SERIAL_FLOPPY
        jnc     .founddpt
;
; If not found above with FindDPT_ToDSDIforSerialDevice, DI will point to the DPT after the last hard disk DPT
; So, if there was a previously found floppy disk, DI will point to that DPT and we use that value for the slave.
;
        cmp     byte [RAMVARS.xlateVars+XLATEVARS.bFlopCntAndFirst], 0
        jz      .notfounddpt
.founddpt:
%else
        jc      .notfounddpt
%endif
        mov     ax, [di+DPT_SERIAL.wSerialPortAndBaud]
.notfounddpt:

        test    bh, FLG_DRVNHEAD_DRV
        jz      .master

        test    ax,ax           ; Take care of the case that is different between master and slave.
        jz      .error          

; fall-through
.master:
        test    dx,dx
        jnz     .identifyDeviceInDX

        xchg    dx, ax          ;  move ax to dx (move previously found serial drive to dx, could be zero)

.identifyDeviceInDX:    
        jmp     SerialServerScan_ScanForServer

.error:
        stc
        ret