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nuttx/drivers/serial/serial_io.c

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/************************************************************************************
* drivers/serial/serial_io.c
*
* Copyright (C) 2007-2009, 2011, 2015, 2018 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
************************************************************************************/
/************************************************************************************
* Included Files
************************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <semaphore.h>
#include <debug.h>
#include <nuttx/serial/serial.h>
/************************************************************************************
* Public Functions
************************************************************************************/
/************************************************************************************
* Name: uart_xmitchars
*
* Description:
* This function is called from the UART interrupt handler when an interrupt
* is received indicating that there is more space in the transmit FIFO. This
* function will send characters from the tail of the xmit buffer while the driver
* write() logic adds data to the head of the xmit buffer.
*
************************************************************************************/
void uart_xmitchars(FAR uart_dev_t *dev)
{
uint16_t nbytes = 0;
/* Send while we still have data in the TX buffer & room in the fifo */
while (dev->xmit.head != dev->xmit.tail && uart_txready(dev))
{
/* Send the next byte */
uart_send(dev, dev->xmit.buffer[dev->xmit.tail]);
nbytes++;
/* Increment the tail index */
if (++(dev->xmit.tail) >= dev->xmit.size)
{
dev->xmit.tail = 0;
}
}
/* When all of the characters have been sent from the buffer disable the TX
* interrupt.
*
* Potential bug? If nbytes == 0 && (dev->xmit.head == dev->xmit.tail) &&
* dev->xmitwaiting == true, then disabling the TX interrupt will leave
* the uart_write() logic waiting to TX to complete with no TX interrupts.
* Can that happen?
*/
if (dev->xmit.head == dev->xmit.tail)
{
uart_disabletxint(dev);
}
/* If any bytes were removed from the buffer, inform any waiters there there is
* space available.
*/
if (nbytes)
{
uart_datasent(dev);
}
}
/************************************************************************************
* Name: uart_receivechars
*
* Description:
* This function is called from the UART interrupt handler when an interrupt
* is received indicating that are bytes available in the receive fifo. This
* function will add chars to head of receive buffer. Driver read() logic will
* take characters from the tail of the buffer.
*
************************************************************************************/
void uart_recvchars(FAR uart_dev_t *dev)
{
FAR struct uart_buffer_s *rxbuf = &dev->recv;
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
unsigned int watermark;
#endif
unsigned int status;
int nexthead = rxbuf->head + 1;
#if defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGSTP)
int signo = 0;
#endif
uint16_t nbytes = 0;
if (nexthead >= rxbuf->size)
{
nexthead = 0;
}
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
/* Pre-calculate the watermark level that we will need to test against. */
watermark = (CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK * rxbuf->size) / 100;
#endif
/* Loop putting characters into the receive buffer until there are no further
* characters to available.
*/
while (uart_rxavailable(dev))
{
bool is_full = (nexthead == rxbuf->tail);
char ch;
#ifdef CONFIG_SERIAL_IFLOWCONTROL
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
unsigned int nbuffered;
/* How many bytes are buffered */
if (rxbuf->head >= rxbuf->tail)
{
nbuffered = rxbuf->head - rxbuf->tail;
}
else
{
nbuffered = rxbuf->size - rxbuf->tail + rxbuf->head;
}
/* Is the level now above the watermark level that we need to report? */
if (nbuffered >= watermark)
{
/* Let the lower level driver know that the watermark level has been
* crossed. It will probably activate RX flow control.
*/
if (uart_rxflowcontrol(dev, nbuffered, true))
{
/* Low-level driver activated RX flow control, exit loop now. */
break;
}
}
#else
/* Check if RX buffer is full and allow serial low-level driver to pause
* processing. This allows proper utilization of hardware flow control.
*/
if (is_full)
{
if (uart_rxflowcontrol(dev, rxbuf->size, true))
{
/* Low-level driver activated RX flow control, exit loop now. */
break;
}
}
#endif
#endif
/* Get this next character from the hardware */
ch = uart_receive(dev, &status);
#ifdef CONFIG_TTY_SIGINT
/* Is this the special character that will generate the SIGINT signal? */
if (dev->pid >= 0 && ch == CONFIG_TTY_SIGINT_CHAR)
{
/* Yes.. note that the kill is needed and do not put the character
* into the Rx buffer. It should not be read as normal data.
*/
signo = SIGINT;
}
else
#endif
#ifdef CONFIG_TTY_SIGSTP
/* Is this the special character that will generate the SIGSTP signal? */
if (dev->pid >= 0 && ch == CONFIG_TTY_SIGSTP_CHAR)
{
#ifdef CONFIG_TTY_SIGINT
/* Give precedence to SIGINT */
if (signo == 0)
#endif
{
/* Note that the kill is needed and do not put the character
* into the Rx buffer. It should not be read as normal data.
*/
signo = SIGSTP;
}
}
else
#endif
/* If the RX buffer becomes full, then the serial data is discarded. This is
* necessary because on most serial hardware, you must read the data in order
* to clear the RX interrupt. An option on some hardware might be to simply
* disable RX interrupts until the RX buffer becomes non-FULL. However, that
* would probably just cause the overrun to occur in hardware (unless it has
* some large internal buffering).
*/
if (!is_full)
{
/* Add the character to the buffer */
rxbuf->buffer[rxbuf->head] = ch;
nbytes++;
/* Increment the head index */
rxbuf->head = nexthead;
if (++nexthead >= rxbuf->size)
{
nexthead = 0;
}
}
}
/* If any bytes were added to the buffer, inform any waiters there is new
* incoming data available.
*/
if (nbytes)
{
uart_datareceived(dev);
}
#if defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGSTP)
/* Send the signal if necessary */
if (signo != 0)
{
kill(dev->pid, signo);
uart_reset_sem(dev);
}
#endif
}
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