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nuttx/drivers/serial/serial.c
patacongo b7a1b00c08 drivers/serial/serial.c open, read, write, and poll methods will not return a short transfer or an EINTR error if a signal is received while waiting (only) 
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5022 42af7a65-404d-4744-a932-0658087f49c3
2012-08-12 17:37:04 +00:00

949 lines
26 KiB
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/************************************************************************************
* drivers/serial/serial.c
*
* Copyright (C) 2007-2009, 2011-2012 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 <stdbool.h>
#include <unistd.h>
#include <semaphore.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/irq.h>
#include <nuttx/arch.h>
#include <nuttx/fs/fs.h>
#include <nuttx/serial/serial.h>
/************************************************************************************
* Definitions
************************************************************************************/
/* The architecture must provide up_putc for this driver */
#ifndef CONFIG_ARCH_LOWPUTC
# error "Architecture must provide up_putc() for this driver"
#endif
#define uart_putc(ch) up_putc(ch)
#define HALF_SECOND_MSEC 500
#define HALF_SECOND_USEC 500000L
/************************************************************************************
* Private Types
************************************************************************************/
/************************************************************************************
* Private Function Prototypes
************************************************************************************/
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);
#ifndef CONFIG_DISABLE_POLL
static int uart_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup);
#endif
/************************************************************************************
* Private Variables
************************************************************************************/
static const struct file_operations g_serialops =
{
uart_open, /* open */
uart_close, /* close */
uart_read, /* read */
uart_write, /* write */
0, /* seek */
uart_ioctl /* ioctl */
#ifndef CONFIG_DISABLE_POLL
, uart_poll /* poll */
#endif
};
/************************************************************************************
* Private Functions
************************************************************************************/
/************************************************************************************
* Name: uart_takesem
************************************************************************************/
static int uart_takesem(FAR sem_t *sem, bool errout)
{
/* Loop, ignoring interrupts, until we have successfully acquired the semaphore */
while (sem_wait(sem) != OK)
{
/* The only case that an error should occur here is if the wait was awakened
* by a signal.
*/
ASSERT(get_errno() == EINTR);
/* When the signal is received, should we errout? Or should we just continue
* waiting until we have the semaphore?
*/
if (errout)
{
return -EINTR;
}
}
return OK;
}
/************************************************************************************
* Name: uart_givesem
************************************************************************************/
#define uart_givesem(sem) (void)sem_post(sem)
/****************************************************************************
* Name: uart_pollnotify
****************************************************************************/
#ifndef CONFIG_DISABLE_POLL
static void uart_pollnotify(FAR uart_dev_t *dev, pollevent_t eventset)
{
int i;
for (i = 0; i < CONFIG_SERIAL_NPOLLWAITERS; i++)
{
struct pollfd *fds = dev->fds[i];
if (fds)
{
fds->revents |= (fds->events & eventset);
if (fds->revents != 0)
{
fvdbg("Report events: %02x\n", fds->revents);
sem_post(fds->sem);
}
}
}
}
#else
# define uart_pollnotify(dev,event)
#endif
/************************************************************************************
* Name: uart_putxmitchar
************************************************************************************/
static int uart_putxmitchar(FAR uart_dev_t *dev, int ch)
{
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 (;;)
{
if (nexthead != dev->xmit.tail)
{
dev->xmit.buffer[dev->xmit.head] = ch;
dev->xmit.head = nexthead;
return OK;
}
else
{
/* Inform the interrupt level logic that we are waiting. This and
* the following steps must be atomic.
*/
flags = irqsave();
dev->xmitwaiting = true;
/* 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.
*/
uart_enabletxint(dev);
ret = uart_takesem(&dev->xmitsem, true);
uart_disabletxint(dev);
irqrestore(flags);
/* 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;
}
}
}
/* We won't get here */
return OK;
}
/************************************************************************************
* Name: uart_irqwrite
************************************************************************************/
static 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++;
uart_putc(ch);
/* If this is the console, then we should replace LF with LF-CR */
if (ch == '\n')
{
uart_putc('\r');
}
}
return ret;
}
/************************************************************************************
* Name: uart_write
************************************************************************************/
static ssize_t uart_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
{
FAR struct inode *inode = filep->f_inode;
FAR uart_dev_t *dev = inode->i_private;
ssize_t nread = buflen;
int ret;
/* We may receive console writes through this path from
* interrupt handlers and from debug output in the IDLE task!
* In these cases, we will need to do things a little
* differently.
*/
if (up_interrupt_context() || getpid() == 0)
{
if (dev->isconsole)
{
irqstate_t flags = irqsave();
ret = uart_irqwrite(dev, buffer, buflen);
irqrestore(flags);
return ret;
}
else
{
return ERROR;
}
}
/* Only one user can access dev->xmit.head at a time */
ret = (ssize_t)uart_takesem(&dev->xmit.sem, true);
if (ret < 0)
{
/* A signal received while waiting for access to the xmit.head 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 transmit buffer.
* we add data to the head of the buffer; uart_xmitchars takes the
* data from the end of the buffer.
*/
uart_disabletxint(dev);
for (; buflen; buflen--)
{
int ch = *buffer++;
/* If this is the console, then we should replace LF with CR-LF */
ret = OK;
if (dev->isconsole && ch == '\n')
{
ret = uart_putxmitchar(dev, '\r');
}
/* Put the character into the transmit buffer */
if (ret == OK)
{
ret = uart_putxmitchar(dev, ch);
}
/* Were we awakened by a signal? That should be the only condition that
* uart_putxmitchar() should return an error.
*/
if (ret < 0)
{
/* POSIX requires that we return -1 and errno set if no data was
* transferred. Otherwise, we return the number of bytes in the
* interrupted transfer.
*/
if (buflen < nread)
{
/* Some data was transferred. Return the number of bytes that were
* successfully transferred.
*/
nread -= buflen;
}
else
{
/* No data was transferred. Return -EINTR. The VFS layer will
* set the errno value appropriately).
*/
nread = -EINTR;
}
break;
}
}
if (dev->xmit.head != dev->xmit.tail)
{
uart_enabletxint(dev);
}
uart_givesem(&dev->xmit.sem);
return nread;
}
/************************************************************************************
* 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;
irqstate_t flags;
ssize_t recvd = 0;
int16_t tail;
int ret;
/* Only one user can access dev->recv.tail at a time */
ret = uart_takesem(&dev->recv.sem, true);
if (ret < 0)
{
/* A signal received while waiting for access to the recv.tail will avort
* 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 (recvd < buflen)
{
/* Check if there is more data to return in the circular buffer.
* NOTE: Rx interrupt handling logic may aynchronously 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 = dev->recv.tail;
if (dev->recv.head != tail)
{
/* Take the next character from the tail of the buffer */
*buffer++ = dev->recv.buffer[tail];
recvd++;
/* Increment the tail index. Most operations are done using the
* local variable 'tail' so that the final dev->recv.tail update
* is atomic.
*/
if (++tail >= dev->recv.size)
{
tail = 0;
}
dev->recv.tail = tail;
}
#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)
{
/* 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;
}
/* 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)
{
/* 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 Rx interrupts and test again... */
uart_disablerxint(dev);
/* If the Rx ring buffer still empty? Bytes may have been addded
* between the last time that we checked and when we disabled Rx
* interrupts.
*/
if (dev->recv.head == dev->recv.tail)
{
/* Yes.. the buffer is still empty. Wait for some characters
* to be received into the buffer with the RX interrupt re-
* enabled. All interrupts are disabled briefly to assure
* that the following operations are atomic.
*/
flags = irqsave();
dev->recvwaiting = true;
uart_enablerxint(dev);
/* Now wait with the Rx interrupt re-enabled. NuttX will
* automatically re-enable global interrupts when this thread
* goes to sleep.
*/
ret = uart_takesem(&dev->recvsem, true);
irqrestore(flags);
/* Was a signal received while waiting for data to be received? */
if (ret < 0)
{
/* POSIX requires that we return after a signal is received.
* If some bytes were read, we need to return the number of bytes
* read; if no bytes were read, we need to return -1 with the
* errno set correctly.
*/
if (recvd == 0)
{
/* No bytes were read, return -EINTR (the VFS layer will
* set the errno value appropriately.
*/
recvd = -EINTR;
}
break;
}
}
else
{
/* No... the ring buffer is no longer empty. Just re-enable Rx
* interrupts and accept the new data on the next time through
* the loop.
*/
uart_enablerxint(dev);
}
}
}
uart_givesem(&dev->recv.sem);
return recvd;
}
/************************************************************************************
* Name: uart_ioctl
************************************************************************************/
static int uart_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct inode *inode = filep->f_inode;
FAR uart_dev_t *dev = inode->i_private;
return dev->ops->ioctl(filep, cmd, arg);
}
/****************************************************************************
* Name: uart_poll
****************************************************************************/
#ifndef CONFIG_DISABLE_POLL
int uart_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
{
FAR struct inode *inode = filep->f_inode;
FAR uart_dev_t *dev = inode->i_private;
pollevent_t eventset;
int ndx;
int ret;
int i;
/* Some sanity checking */
#if CONFIG_DEBUG
if (!dev || !fds)
{
return -ENODEV;
}
#endif
/* Are we setting up the poll? Or tearing it down? */
ret = uart_takesem(&dev->pollsem, true);
if (ret < 0)
{
/* A signal received while waiting for access to the poll data
* will abort the operation.
*/
return ret;
}
if (setup)
{
/* This is a request to set up the poll. Find an available
* slot for the poll structure reference
*/
for (i = 0; i < CONFIG_SERIAL_NPOLLWAITERS; i++)
{
/* Find an available slot */
if (!dev->fds[i])
{
/* Bind the poll structure and this slot */
dev->fds[i] = fds;
fds->priv = &dev->fds[i];
break;
}
}
if (i >= CONFIG_SERIAL_NPOLLWAITERS)
{
fds->priv = NULL;
ret = -EBUSY;
goto errout;
}
/* Should we immediately notify on any of the requested events?
* First, check if the xmit buffer is full.
*
* Get exclusive access to the xmit buffer indices. NOTE: that we do not
* let this wait be interrupted by a signal (we probably should, but that
* would be a little awkward).
*/
eventset = 0;
(void)uart_takesem(&dev->xmit.sem, false);
ndx = dev->xmit.head + 1;
if (ndx >= dev->xmit.size)
{
ndx = 0;
}
if (ndx != dev->xmit.tail)
{
eventset |= POLLOUT;
}
uart_givesem(&dev->xmit.sem);
/* Check if the receive buffer is empty
*
* Get exclusive access to the recv buffer indices. NOTE: that we do not
* let this wait be interrupted by a signal (we probably should, but that
* would be a little awkward).
*/
(void)uart_takesem(&dev->recv.sem, false);
if (dev->recv.head != dev->recv.tail)
{
eventset |= POLLIN;
}
uart_givesem(&dev->recv.sem);
if (eventset)
{
uart_pollnotify(dev, eventset);
}
}
else if (fds->priv)
{
/* This is a request to tear down the poll. */
struct pollfd **slot = (struct pollfd **)fds->priv;
#ifdef CONFIG_DEBUG
if (!slot)
{
ret = -EIO;
goto errout;
}
#endif
/* Remove all memory of the poll setup */
*slot = NULL;
fds->priv = NULL;
}
errout:
uart_givesem(&dev->pollsem);
return ret;
}
#endif
/************************************************************************************
* 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.
*/
(void)uart_takesem(&dev->closesem, false);
if (dev->open_count > 1)
{
dev->open_count--;
uart_givesem(&dev->closesem);
return OK;
}
/* There are no more references to the port */
dev->open_count = 0;
/* Stop accepting input */
uart_disablerxint(dev);
/* Now we wait for the transmit buffer to clear */
while (dev->xmit.head != dev->xmit.tail)
{
#ifndef CONFIG_DISABLE_SIGNALS
usleep(HALF_SECOND_USEC);
#else
up_mdelay(HALF_SECOND_MSEC);
#endif
}
/* And wait for the TX fifo to drain */
while (!uart_txempty(dev))
{
#ifndef CONFIG_DISABLE_SIGNALS
usleep(HALF_SECOND_USEC);
#else
up_mdelay(HALF_SECOND_MSEC);
#endif
}
/* Free the IRQ and disable the UART */
flags = irqsave(); /* Disable interrupts */
uart_detach(dev); /* Detach interrupts */
if (!dev->isconsole) /* Check for the serial console UART */
{
uart_shutdown(dev); /* Disable the UART */
}
irqrestore(flags);
uart_givesem(&dev->closesem);
return OK;
}
/************************************************************************************
* Name: uart_open
*
* Description:
* This routine is called whenever a serial port is opened.
*
************************************************************************************/
static int uart_open(FAR struct file *filep)
{
struct inode *inode = filep->f_inode;
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 = uart_takesem(&dev->closesem, true);
if (ret < 0)
{
/* A signal received while waiting for the last close operation. */
return ret;
}
/* 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_sem;
}
/* Check if this is the first time that the driver has been opened. */
if (tmp == 1)
{
irqstate_t flags = irqsave();
/* 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)
{
irqrestore(flags);
goto errout_with_sem;
}
}
/* 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)
{
uart_shutdown(dev);
irqrestore(flags);
goto errout_with_sem;
}
/* Mark the io buffers empty */
dev->xmit.head = 0;
dev->xmit.tail = 0;
dev->recv.head = 0;
dev->recv.tail = 0;
/* Enable the RX interrupt */
uart_enablerxint(dev);
irqrestore(flags);
}
/* Save the new open count on success */
dev->open_count = tmp;
errout_with_sem:
uart_givesem(&dev->closesem);
return ret;
}
/************************************************************************************
* Public Functions
************************************************************************************/
/************************************************************************************
* Name: uart_register
*
* Description:
* Register serial console and serial ports.
*
************************************************************************************/
int uart_register(FAR const char *path, FAR uart_dev_t *dev)
{
sem_init(&dev->xmit.sem, 0, 1);
sem_init(&dev->recv.sem, 0, 1);
sem_init(&dev->closesem, 0, 1);
sem_init(&dev->xmitsem, 0, 0);
sem_init(&dev->recvsem, 0, 0);
#ifndef CONFIG_DISABLE_POLL
sem_init(&dev->pollsem, 0, 1);
#endif
dbg("Registering %s\n", path);
return register_driver(path, &g_serialops, 0666, dev);
}
/************************************************************************************
* Name: uart_datareceived
*
* Description:
* This function is called from uart_recvchars when new serial data is place in
* the driver's circular buffer. This function will wake-up any stalled read()
* operations that are waiting for incoming data.
*
************************************************************************************/
void uart_datareceived(FAR uart_dev_t *dev)
{
/* Awaken any awaiting read() operations */
if (dev->recvwaiting)
{
dev->recvwaiting = false;
(void)sem_post(&dev->recvsem);
}
/* Notify all poll/select waiters that they can read from the recv buffer */
uart_pollnotify(dev, POLLIN);
}
/************************************************************************************
* Name: uart_datasent
*
* Description:
* This function is called from uart_xmitchars after serial data has been sent,
* freeing up some space in the driver's circular buffer. This function will
* wake-up any stalled write() operations that was waiting for space to buffer
* outgoing data.
*
************************************************************************************/
void uart_datasent(FAR uart_dev_t *dev)
{
if (dev->xmitwaiting)
{
dev->xmitwaiting = false;
(void)sem_post(&dev->xmitsem);
}
/* Notify all poll/select waiters that they can write to xmit buffer */
uart_pollnotify(dev, POLLOUT);
}
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