text: /*
   * FreeRTOS Kernel V10.4.1
   * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of
   * this software and associated documentation files (the "Software"), to deal in
   * the Software without restriction, including without limitation the rights to
   * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   * the Software, and to permit persons to whom the Software is furnished to do so,
   * subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
   * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   * https://www.FreeRTOS.org
   * https://www.github.com/FreeRTOS
   *
   * 1 tab == 4 spaces!
   */
  
  #include <stdint.h>
  
  #include "ns16550.h"
  
  /* register definitions */
  #define REG_RBR		0x00 /* Receiver buffer reg. */
  #define REG_THR		0x00 /* Transmitter holding reg. */
  #define REG_IER		0x01 /* Interrupt enable reg. */
  #define REG_IIR		0x02 /* Interrupt ID reg. */
  #define REG_FCR		0x02 /* FIFO control reg. */
  #define REG_LCR		0x03 /* Line control reg. */
  #define REG_MCR		0x04 /* Modem control reg. */
  #define REG_LSR		0x05 /* Line status reg. */
  #define REG_MSR		0x06 /* Modem status reg. */
  #define REG_SCR		0x07 /* Scratch reg. */
  #define REG_BRDL	0x00 /* Divisor latch (LSB) */
  #define REG_BRDH	0x01 /* Divisor latch (MSB) */
  
  /* Line status */
  #define LSR_DR			0x01 /* Data ready */
  #define LSR_OE			0x02 /* Overrun error */
  #define LSR_PE			0x04 /* Parity error */
  #define LSR_FE			0x08 /* Framing error */
  #define LSR_BI			0x10 /* Break interrupt */
  #define LSR_THRE		0x20 /* Transmitter holding register empty */
  #define LSR_TEMT		0x40 /* Transmitter empty */
  #define LSR_EIRF		0x80 /* Error in RCVR FIFO */
  
  static uint8_t readb( uintptr_t addr )
  {
  	return *( (uint8_t *) addr );
  }
  
  static void writeb( uint8_t b, uintptr_t addr )
  {
  	*( (uint8_t *) addr ) = b;
  }
  
  void vOutNS16550( struct device *dev, unsigned char c )
  {
  	uintptr_t addr = dev->addr;
  
  	while ( (readb( addr + REG_LSR ) & LSR_THRE) == 0 ) {
  		/* busy wait */
  	}
  
  	writeb( c, addr + REG_THR );
  }
  