/*
 * Copyright (c) 1998 Robert Nordier
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are freely
 * permitted provided that the above copyright notice and this
 * paragraph and the following disclaimer are duplicated in all
 * such forms.
 *
 * This software is provided "AS IS" and without any express or
 * implied warranties, including, without limitation, the implied
 * warranties of merchantability and fitness for a particular
 * purpose.
 */

                .set SIO_PRT,SIOPRT             # Base port
                .set SIO_FMT,SIOFMT             # 8N1

                .globl sio_init
                .globl sio_flush
                .globl sio_putc
                .globl sio_getc
                .globl sio_ischar

/* int sio_init(int div) */

sio_init:       pushl %eax
                movw $SIO_PRT+0x3,%dx           # Data format reg
                movb $SIO_FMT|0x80,%al          # Set format
                outb %al,(%dx)                  #  and DLAB
                subb $0x3,%dl                   # Divisor latch reg
                popl %eax
                outw %ax,(%dx)                  #  BPS
                movw $SIO_PRT+0x3,%dx           # Data format reg
                movb $SIO_FMT,%al               # Clear
                outb %al,(%dx)                  #  DLAB
                incl %edx                       # Modem control reg
                movb $0x3,%al                   # Set RTS,
                outb %al,(%dx)                  #  DTR
                incl %edx                       # Line status reg
                # Fallthrough

/* int sio_flush(void) */

sio_flush:      xorl %ecx,%ecx                  # Timeout
                movb $0x80,%ch                  #  counter
sio_flush.1:    call sio_ischar                 # Check for character
                jz sio_flush.2                  # Till none
                loop sio_flush.1                #  or counter is zero
                movb $1, %al                    # Exhausted all tries
sio_flush.2:    ret                             # To caller

/* void sio_putc(int c) */

sio_putc:       pushl %eax
                movw $SIO_PRT+0x5,%dx           # Line status reg
                xor %ecx,%ecx                   # Timeout
                movb $0x40,%ch                  #  counter
sio_putc.1:     inb (%dx),%al                   # Transmitter
                testb $0x20,%al                 #  buffer empty?
                loopz sio_putc.1                # No
                jz sio_putc.2                   # If timeout
                popl %eax                       # Get the character
                subb $0x5,%dl                   # Transmitter hold reg
                outb %al,(%dx)                  # Write character
sio_putc.2:     ret                             # To caller

/* int sio_getc(void) */

sio_getc:       call sio_ischar                 # Character available?
                jz sio_getc                     # No
sio_getc.1:     subb $0x5,%dl                   # Receiver buffer reg
                inb (%dx),%al                   # Read character
                ret                             # To caller

/* int sio_ischar(void) */

sio_ischar:     movw $SIO_PRT+0x5,%dx           # Line status register
                xorl %eax,%eax                  # Zero
                inb (%dx),%al                   # Received data
                andb $0x1,%al                   #  ready?
                ret                             # To caller