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serial.c
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serial.c
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/****************************************************************************
* drivers/serial/serial.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/param.h>
#include <stdint.h>
#include <stdbool.h>
#include <time.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>
#include <spawn.h>
#include <nuttx/irq.h>
#include <nuttx/ascii.h>
#include <nuttx/arch.h>
#include <nuttx/clock.h>
#include <nuttx/sched.h>
#include <nuttx/signal.h>
#include <nuttx/fs/fs.h>
#include <nuttx/cancelpt.h>
#include <nuttx/serial/serial.h>
#include <nuttx/fs/ioctl.h>
#include <nuttx/power/pm.h>
#include <nuttx/wqueue.h>
#include <nuttx/kthread.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Check watermark levels */
#if defined(CONFIG_SERIAL_IFLOWCONTROL) && \
defined(CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS)
# if CONFIG_SERIAL_IFLOWCONTROL_LOWER_WATERMARK < 1
# warning CONFIG_SERIAL_IFLOWCONTROL_LOWER_WATERMARK too small
# endif
# if CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK > 99
# warning CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK too large
# endif
# if CONFIG_SERIAL_IFLOWCONTROL_LOWER_WATERMARK >= CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK
# warning CONFIG_SERIAL_IFLOWCONTROL_LOWER_WATERMARK too large
# warning Must be less than CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK
# endif
#endif
/* Timing */
#define POLL_DELAY_USEC 1000
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/* Write support */
static int uart_putxmitchar(FAR uart_dev_t *dev, int ch,
bool oktoblock);
static inline ssize_t uart_irqwrite(FAR uart_dev_t *dev,
FAR const char *buffer,
size_t buflen);
static int uart_tcdrain(FAR uart_dev_t *dev,
bool cancelable, clock_t timeout);
static int uart_tcsendbreak(FAR uart_dev_t *dev,
FAR struct file *filep,
unsigned int ms);
/* Character driver methods */
static int uart_open(FAR struct file *filep);
static int uart_close(FAR struct file *filep);
static ssize_t uart_read(FAR struct file *filep,
FAR char *buffer, size_t buflen);
static ssize_t uart_write(FAR struct file *filep,
FAR const char *buffer,
size_t buflen);
static int uart_ioctl(FAR struct file *filep,
int cmd, unsigned long arg);
static int uart_poll(FAR struct file *filep,
FAR struct pollfd *fds, bool setup);
/****************************************************************************
* Public Function Prototypes
****************************************************************************/
#ifdef CONFIG_TTY_LAUNCH_ENTRY
/* Lanch program entry, this must be supplied by the application. */
int CONFIG_TTY_LAUNCH_ENTRYPOINT(int argc, char *argv[]);
#endif
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_serialops =
{
uart_open, /* open */
uart_close, /* close */
uart_read, /* read */
uart_write, /* write */
NULL, /* seek */
uart_ioctl, /* ioctl */
NULL, /* mmap */
NULL, /* truncate */
uart_poll /* poll */
};
#ifdef CONFIG_TTY_LAUNCH
static struct work_s g_serial_work;
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: uart_putxmitchar
****************************************************************************/
static int uart_putxmitchar(FAR uart_dev_t *dev, int ch, bool oktoblock)
{
irqstate_t flags;
int nexthead;
int ret;
/* Increment to see what the next head pointer will be.
* We need to use the "next" head pointer to determine when the circular
* buffer would overrun
*/
nexthead = dev->xmit.head + 1;
if (nexthead >= dev->xmit.size)
{
nexthead = 0;
}
/* Loop until we are able to add the character to the TX buffer. */
for (; ; )
{
/* Check if the TX buffer is full */
if (nexthead != dev->xmit.tail)
{
/* No.. not full. Add the character to the TX buffer and return. */
dev->xmit.buffer[dev->xmit.head] = ch;
dev->xmit.head = nexthead;
return OK;
}
/* The TX buffer is full. Should be block, waiting for the hardware
* to remove some data from the TX buffer?
*/
else if (oktoblock)
{
/* The following steps must be atomic with respect to serial
* interrupt handling.
*/
flags = enter_critical_section();
/* Check again... In certain race conditions an interrupt may
* have occurred between the test at the top of the loop and
* entering the critical section and the TX buffer may no longer
* be full.
*
* NOTE: On certain devices, such as USB CDC/ACM, the entire TX
* buffer may have been emptied in this race condition. In that
* case, the logic would hang below waiting for space in the TX
* buffer without this test.
*/
if (nexthead != dev->xmit.tail)
{
ret = OK;
}
#ifdef CONFIG_SERIAL_REMOVABLE
/* Check if the removable device is no longer connected while we
* have interrupts off. We do not want the transition to occur
* as a race condition before we begin the wait.
*/
else if (dev->disconnected)
{
ret = -ENOTCONN;
}
#endif
else
{
/* Wait for some characters to be sent from the buffer with
* the TX interrupt enabled. When the TX interrupt is enabled,
* uart_xmitchars() should execute and remove some of the data
* from the TX buffer.
*
* NOTE that interrupts will be re-enabled while we wait for
* the semaphore.
*/
#ifdef CONFIG_SERIAL_TXDMA
uart_dmatxavail(dev);
#endif
uart_enabletxint(dev);
ret = nxsem_wait(&dev->xmitsem);
uart_disabletxint(dev);
}
leave_critical_section(flags);
#ifdef CONFIG_SERIAL_REMOVABLE
/* Check if the removable device was disconnected while we were
* waiting.
*/
if (dev->disconnected)
{
return -ENOTCONN;
}
#endif
/* Check if we were awakened by signal. */
if (ret < 0)
{
/* A signal received while waiting for the xmit buffer to
* become non-full will abort the transfer.
*/
return -EINTR;
}
}
/* The caller has request that we not block for data. So return the
* EAGAIN error to signal this situation.
*/
else
{
return -EAGAIN;
}
}
/* We won't get here. Some compilers may complain that this code is
* unreachable.
*/
return OK;
}
/****************************************************************************
* Name: uart_putc
****************************************************************************/
static inline void uart_putc(FAR uart_dev_t *dev, int ch)
{
while (!uart_txready(dev))
{
}
uart_send(dev, ch);
}
/****************************************************************************
* Name: uart_irqwrite
****************************************************************************/
static inline ssize_t uart_irqwrite(FAR uart_dev_t *dev,
FAR const char *buffer,
size_t buflen)
{
ssize_t ret = buflen;
/* Force each character through the low level interface */
for (; buflen; buflen--)
{
int ch = *buffer++;
/* Do output post-processing */
if ((dev->tc_oflag & OPOST) != 0)
{
/* Mapping CR to NL? */
if ((ch == '\r') && (dev->tc_oflag & OCRNL) != 0)
{
ch = '\n';
}
/* Are we interested in newline processing? */
if ((ch == '\n') && (dev->tc_oflag & (ONLCR | ONLRET)) != 0)
{
uart_putc(dev, '\r');
}
}
/* Output the character, using the low-level direct UART interfaces */
uart_putc(dev, ch);
}
return ret;
}
/****************************************************************************
* Name: uart_tcdrain
*
* Description:
* Block further TX input.
* Wait until all data has been transferred from the TX buffer and
* until the hardware TX FIFOs are empty.
*
****************************************************************************/
static int uart_tcdrain(FAR uart_dev_t *dev,
bool cancelable, clock_t timeout)
{
int ret;
/* tcdrain is a cancellation point */
if (cancelable && enter_cancellation_point())
{
#ifdef CONFIG_CANCELLATION_POINTS
/* If there is a pending cancellation, then do not perform
* the wait. Exit now with ECANCELED.
*/
leave_cancellation_point();
return -ECANCELED;
#endif
}
/* Get exclusive access to the to dev->tmit. We cannot permit new data to
* be written while we are trying to flush the old data.
*
* A signal received while waiting for access to the xmit.head will abort
* the operation with EINTR.
*/
ret = nxmutex_lock(&dev->xmit.lock);
if (ret >= 0)
{
irqstate_t flags;
clock_t start;
/* Trigger emission to flush the contents of the tx buffer */
flags = enter_critical_section();
#ifdef CONFIG_SERIAL_REMOVABLE
/* Check if the removable device is no longer connected while we have
* interrupts off. We do not want the transition to occur as a race
* condition before we begin the wait.
*/
if (dev->disconnected)
{
dev->xmit.tail = dev->xmit.head; /* Drop the buffered TX data */
ret = -ENOTCONN;
}
else
#endif
{
/* Continue waiting while the TX buffer is not empty.
*
* NOTE: There is no timeout on the following loop. In
* situations were this loop could hang (with hardware flow
* control, as an example), the caller should call
* tcflush() first to discard this buffered Tx data.
*/
ret = OK;
while (ret >= 0 && dev->xmit.head != dev->xmit.tail)
{
/* Wait for some characters to be sent from the buffer with
* the TX interrupt enabled. When the TX interrupt is
* enabled, uart_xmitchars() should execute and remove some
* of the data from the TX buffer. We may have to wait several
* times for the TX buffer to be entirely emptied.
*
* NOTE that interrupts will be re-enabled while we wait for
* the semaphore.
*/
#ifdef CONFIG_SERIAL_TXDMA
uart_dmatxavail(dev);
#endif
uart_enabletxint(dev);
ret = nxsem_wait(&dev->xmitsem);
uart_disabletxint(dev);
}
}
leave_critical_section(flags);
/* The TX buffer is empty (or an error occurred). But there still may
* be data in the UART TX FIFO. We get no asynchronous indication of
* this event, so we have to do a busy wait poll.
*/
/* Set up for the timeout
*
* REVISIT: This is a kludge. The correct fix would be add an
* interface to the lower half driver so that the tcflush() operation
* all also cause the lower half driver to clear and reset the Tx FIFO.
*/
start = clock_systime_ticks();
if (ret >= 0)
{
while (!uart_txempty(dev))
{
clock_t elapsed;
nxsig_usleep(POLL_DELAY_USEC);
/* Check for a timeout */
elapsed = clock_systime_ticks() - start;
if (elapsed >= timeout)
{
nxmutex_unlock(&dev->xmit.lock);
return -ETIMEDOUT;
}
}
}
nxmutex_unlock(&dev->xmit.lock);
}
if (cancelable)
{
leave_cancellation_point();
}
return ret;
}
/****************************************************************************
* Name: uart_tcsendbreak
*
* Description:
* Request a serial line Break by calling the lower half driver's
* BSD-compatible Break IOCTLs TIOCSBRK and TIOCCBRK, with a sleep of the
* specified duration between them.
*
* Input Parameters:
* dev - Serial device.
* filep - Required for issuing lower half driver IOCTL call.
* ms - If non-zero, duration of the Break in milliseconds; if
* zero, duration is 400 milliseconds.
*
* Returned Value:
* 0 on success or a negated errno value on failure.
*
****************************************************************************/
static int uart_tcsendbreak(FAR uart_dev_t *dev, FAR struct file *filep,
unsigned int ms)
{
int ret;
/* REVISIT: Do we need to perform the equivalent of tcdrain() before
* beginning the Break to avoid corrupting the transmit data? If so, note
* that just calling uart_tcdrain() here would create a race condition,
* since new transmit data could be written after uart_tcdrain() returns
* but before we re-acquire the dev->xmit.lock here. Therefore, we would
* need to refactor the functional portion of uart_tcdrain() to a separate
* function and call it from both uart_tcdrain() and uart_tcsendbreak()
* in critical section and with xmit lock already held.
*/
if (dev->ops->ioctl)
{
ret = nxmutex_lock(&dev->xmit.lock);
if (ret >= 0)
{
/* Request lower half driver to start the Break */
ret = dev->ops->ioctl(filep, TIOCSBRK, 0);
if (ret >= 0)
{
/* Wait 400 ms or the requested Break duration */
nxsig_usleep((ms == 0) ? 400000 : ms * 1000);
/* Request lower half driver to end the Break */
ret = dev->ops->ioctl(filep, TIOCCBRK, 0);
}
}
nxmutex_unlock(&dev->xmit.lock);
}
else
{
/* With no lower half IOCTL, we cannot request Break at all. */
ret = -ENOTTY;
}
return ret;
}
/****************************************************************************
* Name: uart_open
*
* Description:
* This routine is called whenever a serial port is opened.
*
****************************************************************************/
static int uart_open(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR uart_dev_t *dev = inode->i_private;
uint8_t tmp;
int ret;
/* If the port is the middle of closing, wait until the close is finished.
* If a signal is received while we are waiting, then return EINTR.
*/
ret = nxmutex_lock(&dev->closelock);
if (ret < 0)
{
/* A signal received while waiting for the last close operation. */
return ret;
}
#ifdef CONFIG_SERIAL_REMOVABLE
/* If the removable device is no longer connected, refuse to open the
* device. We check this after obtaining the close semaphore because
* we might have been waiting when the device was disconnected.
*/
if (dev->disconnected)
{
ret = -ENOTCONN;
goto errout_with_lock;
}
#endif
/* Start up serial port */
/* Increment the count of references to the device. */
tmp = dev->open_count + 1;
if (tmp == 0)
{
/* More than 255 opens; uint8_t overflows to zero */
ret = -EMFILE;
goto errout_with_lock;
}
/* Check if this is the first time that the driver has been opened. */
if (tmp == 1)
{
irqstate_t flags = enter_critical_section();
/* If this is the console, then the UART has already been
* initialized.
*/
if (!dev->isconsole)
{
/* Perform one time hardware initialization */
ret = uart_setup(dev);
if (ret < 0)
{
leave_critical_section(flags);
goto errout_with_lock;
}
}
/* In any event, we do have to configure for interrupt driven mode of
* operation. Attach the hardware IRQ(s). Hmm.. should shutdown() the
* the device in the rare case that uart_attach() fails, tmp==1, and
* this is not the console.
*/
ret = uart_attach(dev);
if (ret < 0)
{
if (!dev->isconsole)
{
uart_shutdown(dev);
}
leave_critical_section(flags);
goto errout_with_lock;
}
#ifdef CONFIG_SERIAL_RXDMA
/* Notify DMA that there is free space in the RX buffer */
uart_dmarxfree(dev);
#endif
/* Enable the RX interrupt */
uart_enablerxint(dev);
leave_critical_section(flags);
}
/* Save the new open count on success */
dev->open_count = tmp;
errout_with_lock:
nxmutex_unlock(&dev->closelock);
return ret;
}
/****************************************************************************
* Name: uart_close
*
* Description:
* This routine is called when the serial port gets closed.
* It waits for the last remaining data to be sent.
*
****************************************************************************/
static int uart_close(FAR struct file *filep)
{
FAR struct inode *inode = filep->f_inode;
FAR uart_dev_t *dev = inode->i_private;
irqstate_t flags;
/* Get exclusive access to the close semaphore (to synchronize open/close
* operations.
* NOTE: that we do not let this wait be interrupted by a signal.
* Technically, we should, but almost no one every checks the return value
* from close() so we avoid a potential memory leak by ignoring signals in
* this case.
*/
nxmutex_lock(&dev->closelock);
if (dev->open_count > 1)
{
dev->open_count--;
nxmutex_unlock(&dev->closelock);
return OK;
}
/* There are no more references to the port */
dev->open_count = 0;
/* Stop accepting input */
uart_disablerxint(dev);
/* Prevent blocking if the device is opened with O_NONBLOCK */
if ((filep->f_oflags & O_NONBLOCK) == 0)
{
/* Now we wait for the transmit buffer(s) to clear */
uart_tcdrain(dev, false, 4 * TICK_PER_SEC);
}
/* Free the IRQ and disable the UART */
flags = enter_critical_section(); /* Disable interrupts */
uart_detach(dev); /* Detach interrupts */
if (!dev->isconsole) /* Check for the serial console UART */
{
uart_shutdown(dev); /* Disable the UART */
}
leave_critical_section(flags);
/* Wake up read and poll functions */
uart_datareceived(dev);
/* We need to re-initialize the semaphores if this is the last close
* of the device, as the close might be caused by pthread_cancel() of
* a thread currently blocking on any of them.
*/
uart_reset_sem(dev);
nxmutex_unlock(&dev->closelock);
return OK;
}
/****************************************************************************
* Name: uart_read
****************************************************************************/
static ssize_t uart_read(FAR struct file *filep,
FAR char *buffer, size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR uart_dev_t *dev = inode->i_private;
FAR struct uart_buffer_s *rxbuf = &dev->recv;
#ifdef CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS
unsigned int nbuffered;
unsigned int watermark;
#endif
irqstate_t flags;
ssize_t recvd = 0;
bool echoed = false;
int16_t tail;
char ch;
int ret;
/* Only one user can access rxbuf->tail at a time */
ret = nxmutex_lock(&dev->recv.lock);
if (ret < 0)
{
/* A signal received while waiting for access to the recv.tail will
* abort the transfer. After the transfer has started, we are
* committed and signals will be ignored.
*/
return ret;
}
/* Loop while we still have data to copy to the receive buffer.
* we add data to the head of the buffer; uart_xmitchars takes the
* data from the end of the buffer.
*/
while ((size_t)recvd < buflen)
{
#ifdef CONFIG_SERIAL_REMOVABLE
/* If the removable device is no longer connected, refuse to read any
* further from the device.
*/
if (dev->disconnected)
{
if (recvd == 0)
{
recvd = -ENOTCONN;
}
break;
}
#endif
/* Check if there is more data to return in the circular buffer.
* NOTE: Rx interrupt handling logic may asynchronously increment
* the head index but must not modify the tail index. The tail
* index is only modified in this function. Therefore, no
* special handshaking is required here.
*
* The head and tail pointers are 16-bit values. The only time that
* the following could be unsafe is if the CPU made two non-atomic
* 8-bit accesses to obtain the 16-bit head index.
*/
tail = rxbuf->tail;
if (rxbuf->head != tail)
{
/* Take the next character from the tail of the buffer */
ch = rxbuf->buffer[tail];
/* Increment the tail index. Most operations are done using the
* local variable 'tail' so that the final rxbuf->tail update
* is atomic.
*/
if (++tail >= rxbuf->size)
{
tail = 0;
}
rxbuf->tail = tail;
/* Do input processing if any is enabled */
if (dev->tc_iflag & (INLCR | IGNCR | ICRNL))
{
/* \n -> \r or \r -> \n translation? */
if ((ch == '\n') && (dev->tc_iflag & INLCR))
{
ch = '\r';
}
else if ((ch == '\r') && (dev->tc_iflag & ICRNL))
{
ch = '\n';
}
/* Discarding \r ? */
if ((ch == '\r') && (dev->tc_iflag & IGNCR))
{
continue;
}
}
/* Specifically not handled:
*
* All of the local modes; echo, line editing, etc.
* Anything to do with break or parity errors.
* ISTRIP - we should be 8-bit clean.
* IUCLC - Not Posix
* IXON/OXOFF - no xon/xoff flow control.
*/
/* Store the received character */
*buffer++ = ch;
recvd++;
if (dev->tc_lflag & ECHO)
{
/* Check for the beginning of a VT100 escape sequence, 3 byte */
if (ch == ASCII_ESC)
{
/* Mark that we should skip 2 more bytes */
dev->escape = 2;
continue;
}
else if (dev->escape == 2 && ch != ASCII_LBRACKET)
{
/* It's not an <esc>[x 3 byte sequence, show it */
dev->escape = 0;
}
else if (dev->escape > 0)
{
/* Skipping character count down */
if (dev->escape-- > 0)
{
continue;
}
}
/* Echo if the character is not a control byte */
if (!iscntrl(ch & 0xff) || ch == '\n')
{
if (ch == '\n')
{
uart_putxmitchar(dev, '\r', true);
}
uart_putxmitchar(dev, ch, true);
/* Mark the tx buffer have echoed content here,
* to avoid the tx buffer is empty such as special escape
* sequence received, but enable the tx interrupt.
*/
echoed = true;
}
}
}
#ifdef CONFIG_DEV_SERIAL_FULLBLOCKS
/* No... then we would have to wait to get receive more data.
* If the user has specified the O_NONBLOCK option, then just
* return what we have.
*/
else if ((filep->f_oflags & O_NONBLOCK) != 0)
{
/* If nothing was transferred, then return the -EAGAIN
* error (not zero which means end of file).
*/
if (recvd < 1)
{
recvd = -EAGAIN;
}
break;
}
#else
/* No... the circular buffer is empty. Have we returned anything
* to the caller?
*/
else if (recvd > 0)
{
/* Yes.. break out of the loop and return the number of bytes
* received up to the wait condition.
*/
break;
}
else if (filep->f_inode == 0)
{
/* File has been closed.
* Descriptor is not valid.
*/
recvd = -EBADFD;
break;
}
/* No... then we would have to wait to get receive some data.
* If the user has specified the O_NONBLOCK option, then do not
* wait.
*/
else if ((filep->f_oflags & O_NONBLOCK) != 0)
{
/* Break out of the loop returning -EAGAIN */
recvd = -EAGAIN;
break;
}
#endif
/* Otherwise we are going to have to wait for data to arrive */
else
{
/* Disable all interrupts and test again... */
flags = enter_critical_section();
/* Disable Rx interrupts and test again... */
uart_disablerxint(dev);
/* If the Rx ring buffer still empty? Bytes may have been added
* between the last time that we checked and when we disabled
* interrupts.
*/
if (rxbuf->head == rxbuf->tail)
{
/* Yes.. the buffer is still empty. We will need to wait for
* additional data to be received.
*/
#ifdef CONFIG_SERIAL_RXDMA
/* Notify DMA that there is free space in the RX buffer */
uart_dmarxfree(dev);
#endif
/* Wait with the RX interrupt re-enabled. All interrupts are
* disabled briefly to assure that the following operations
* are atomic.
*/
/* Re-enable UART Rx interrupts */
uart_enablerxint(dev);
/* Check again if the RX buffer is empty. The UART driver
* might have buffered data received between disabling the
* RX interrupt and entering the critical section. Some