Add poll method to serial drivers

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1268 42af7a65-404d-4744-a932-0658087f49c3

8 files changed, 401 insertions, 108 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 32760238a..f6e64259c 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -565,6 +565,6 @@
 
 0.3.19 2008-xx-xx Gregory Nutt <spudmonkey@racsa.co.cr>
 	* Add poll() and select() APIs (in the initial check-in, these work only with character devices) 
-	* Add poll() methods to /dev/null, /dev/zero, pipes, and fifos.
+	* Add poll() methods to /dev/null, /dev/zero, pipes, fifos, and serial drivers.
 	* Add examples/poll for testing poll() and select()
 
diff --git a/nuttx/Documentation/NuttX.html b/nuttx/Documentation/NuttX.html
index e149f42a8..cf3e9603d 100644
--- a/nuttx/Documentation/NuttX.html
+++ b/nuttx/Documentation/NuttX.html
@@ -1201,7 +1201,7 @@ buildroot-0.1.2 2007-11-06 &lt;spudmonkey@racsa.co.cr&gt
 <pre><ul>
 nuttx-0.3.19 2008-xx-xx Gregory Nutt &lt;spudmonkey@racsa.co.cr&gt;
 	* Add poll() and select() APIs (in the initial check-in, these work only with character devices) 
-	* Add poll() methods to /dev/null, /dev/zero, pipes, and fifos.
+	* Add poll() methods to /dev/null, /dev/zero, pipes, fifos, and serial drivers.
 	* Add examples/poll for testing poll() and select()
 
 pascal-0.1.3 2008-xx-xx Gregory Nutt &lt;spudmonkey@racsa.co.cr&gt;
diff --git a/nuttx/arch/sim/src/up_devconsole.c b/nuttx/arch/sim/src/up_devconsole.c
index 6bf733f71..58fa21e3b 100644
--- a/nuttx/arch/sim/src/up_devconsole.c
+++ b/nuttx/arch/sim/src/up_devconsole.c
@@ -53,6 +53,9 @@
 
 static ssize_t devconsole_read(struct file *, char *, size_t);
 static ssize_t devconsole_write(struct file *, const char *, size_t);
+#ifndef CONFIG_DISABLE_POLL
+static int     devconsole_poll(FAR struct file *filep, FAR struct pollfd *fds);
+#endif
 
 /****************************************************************************
  * Private Data
@@ -62,14 +65,16 @@ static struct file_operations devconsole_fops =
 {
   .read		= devconsole_read,
   .write	= devconsole_write,
+#ifndef CONFIG_DISABLE_POLL
+  .poll         = devconsole_poll,
+#endif
 };
 
 /****************************************************************************
  * Private Functions
  ****************************************************************************/
 
-
- static ssize_t devconsole_read(struct file *filp, char *buffer, size_t len)
+static ssize_t devconsole_read(struct file *filp, char *buffer, size_t len)
 {
   return up_hostread(buffer, len);
 }
@@ -79,6 +84,11 @@ static ssize_t devconsole_write(struct file *filp, const char *buffer, size_t le
   return up_hostwrite(buffer, len);
 }
 
+static int devconsole_poll(FAR struct file *filep, FAR struct pollfd *fds)
+{
+  return OK;
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
diff --git a/nuttx/drivers/serial.c b/nuttx/drivers/serial.c
index 366c7a208..2939bf61f 100644
--- a/nuttx/drivers/serial.c
+++ b/nuttx/drivers/serial.c
@@ -44,6 +44,7 @@
 #include <semaphore.h>
 #include <string.h>
 #include <fcntl.h>
+#include <poll.h>
 #include <errno.h>
 #include <debug.h>
 
@@ -77,6 +78,9 @@ 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);
+#endif
 
 /************************************************************************************
  * Private Variables
@@ -89,8 +93,10 @@ struct file_operations g_serialops =
   uart_read,  /* read */
   uart_write, /* write */
   0,          /* seek */
-  uart_ioctl, /* ioctl */
-  0           /* poll */
+  uart_ioctl  /* ioctl */
+#ifndef CONFIG_DISABLE_POLL
+  , uart_poll /* poll */
+#endif
 };
 
 /************************************************************************************
@@ -119,6 +125,33 @@ static void uart_takesem(FAR sem_t *sem)
 
 #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_DEV_CONSOLE_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
  ************************************************************************************/
@@ -340,6 +373,98 @@ static int uart_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
   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)
+{
+  FAR struct inode *inode = filep->f_inode;
+  FAR uart_dev_t   *dev   = inode->i_private;
+  pollevent_t       eventset;
+  int               ndx;
+  int               i;
+
+  /* Some sanity checking */
+#if CONFIG_DEBUG
+  if (!dev)
+    {
+      return -ENODEV;
+    }
+#endif
+
+  /* Find an available slot for the poll structure reference */
+
+  uart_takesem(&dev->pollsem);
+  for (i = 0; i < CONFIG_DEV_CONSOLE_NPOLLWAITERS; i++)
+    {
+      /* Find the slot with the value equal to filep->f_priv.  If there
+       * is not previously installed poll structure, then f_priv will
+       * be NULL and we will find the first unused slot.  If f_priv is
+       * is non-NULL, then we will find the slot that was used for the
+       * previous setup.
+       */
+
+      if (dev->fds[i] == filep->f_priv)
+        {
+          dev->fds[i] = fds;
+          break;
+        }
+    }
+
+  if (i >= CONFIG_DEV_CONSOLE_NPOLLWAITERS)
+    {
+      DEBUGASSERT(fds == NULL);
+      return -EBUSY;
+    }
+
+  /* Set or clear the poll event structure reference in the 'struct file'
+   * private data.
+   */
+
+  filep->f_priv = fds;
+
+  /* Check if we should immediately notify on any of the requested events */
+
+  if (fds)
+    {
+      /* Check if the xmit buffer is full. */
+
+      eventset = 0;
+
+      uart_takesem(&dev->xmit.sem);
+      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 */
+
+      uart_takesem(&dev->recv.sem);
+      if (dev->recv.head != dev->recv.tail)
+       {
+         eventset |= POLLIN;
+       }
+      uart_givesem(&dev->recv.sem);
+
+      if (eventset)
+        {
+          uart_pollnotify(dev, eventset);
+        }
+    }
+
+  uart_givesem(&dev->pollsem);
+  return OK;
+}
+#endif
+
 /************************************************************************************
  * Name: uart_close
  *
@@ -513,7 +638,62 @@ int uart_register(FAR const char *path, FAR uart_dev_t *dev)
   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);
+}
+
+
diff --git a/nuttx/drivers/serialirq.c b/nuttx/drivers/serialirq.c
index f7503e4cc..d1a18b257 100644
--- a/nuttx/drivers/serialirq.c
+++ b/nuttx/drivers/serialirq.c
@@ -80,6 +80,8 @@
 
 void uart_xmitchars(FAR uart_dev_t *dev)
 {
+  uint16 nbytes = 0;
+
   /* Send while we still have data & room in the fifo */
 
   while (dev->xmit.head != dev->xmit.tail && uart_txready(dev))
@@ -87,6 +89,7 @@ void uart_xmitchars(FAR uart_dev_t *dev)
       /* Send the next byte */
 
       uart_send(dev, dev->xmit.buffer[dev->xmit.tail]);
+      nbytes++;
 
       /* Increment the tail index */
 
@@ -94,16 +97,6 @@ void uart_xmitchars(FAR uart_dev_t *dev)
         {
           dev->xmit.tail = 0;
         }
-
-      /* A byte was removed from the buffer.  Inform any waiters
-       * there there is space available.
-       */
-
-      if (dev->xmitwaiting)
-        {
-          dev->xmitwaiting = FALSE;
-          (void)sem_post(&dev->xmitsem);
-        }
     }
 
   /* When all of the characters have been sent from the buffer
@@ -114,6 +107,15 @@ void uart_xmitchars(FAR uart_dev_t *dev)
     {
       uart_disabletxint(dev);
     }
+
+  /* If any bytes were removed from the buffer, inform any waiters
+   * there there is space available.
+   */
+
+  if (nbytes)
+    {
+      uart_datasent(dev);
+    }
 }
 
 /************************************************************************************
@@ -131,6 +133,7 @@ void uart_recvchars(FAR uart_dev_t *dev)
 {
   unsigned int status;
   int nexthead = dev->recv.head + 1;
+  uint16 nbytes = 0;
 
   if (nexthead >= dev->recv.size)
     {
@@ -146,6 +149,7 @@ void uart_recvchars(FAR uart_dev_t *dev)
       /* Add the character to the buffer */
 
       dev->recv.buffer[dev->recv.head] = uart_receive(dev, &status);
+      nbytes++;
 
       /* Increment the head index */
 
@@ -154,18 +158,15 @@ void uart_recvchars(FAR uart_dev_t *dev)
         {
            nexthead = 0;
         }
+    }
 
-      /* A character was added... if there is a thread waiting for more data, then
-       * post the recvsem semaphore to wake it up. NOTE: There is a logic error in
-       * the above looping logic: If nexthead == dev->recv.tail on entry and
-       * recvwaiting is true, the recvsem will never get posted!
-       */
+  /* If any bytes were added to the buffer, inform any waiters
+   * there there is new incoming data available.
+   */
 
-      if (dev->recvwaiting)
-        {
-          dev->recvwaiting = FALSE;
-          (void)sem_post(&dev->recvsem);
-        }
+  if (nbytes)
+    {
+      uart_datareceived(dev);
     }
 }
 
diff --git a/nuttx/drivers/usbdev/usbdev_serial.c b/nuttx/drivers/usbdev/usbdev_serial.c
index 4b32ac052..116accc57 100644
--- a/nuttx/drivers/usbdev/usbdev_serial.c
+++ b/nuttx/drivers/usbdev/usbdev_serial.c
@@ -526,14 +526,6 @@ static uint16 usbclass_fillrequest(FAR struct usbser_dev_s *priv, char *reqbuf,
         {
           xmit->tail = 0;
         }
-
-      /* Check if we have to wake up the serial driver */
-
-      if (serdev->xmitwaiting)
-        {
-          serdev->xmitwaiting = FALSE;
-          sem_post(&serdev->xmitsem);
-        }
     }
 
   /* When all of the characters have been sent from the buffer
@@ -545,6 +537,15 @@ static uint16 usbclass_fillrequest(FAR struct usbser_dev_s *priv, char *reqbuf,
       uart_disabletxint(serdev);
     }
 
+  /* If any bytes were removed from the buffer, inform any waiters
+   * there there is space available.
+   */
+
+  if (nbytes)
+    {
+      uart_datasent(serdev);
+    }
+
   irqrestore(flags);
   return nbytes;
 }
@@ -651,6 +652,7 @@ static inline int usbclass_recvpacket(FAR struct usbser_dev_s *priv,
   FAR struct uart_buffer_s *recv = &serdev->recv;
   uint16 currhead;
   uint16 nexthead;
+  uint16 nbytes = 0;
 
   /* Get the next head index. During the time that RX interrupts are disabled, the
    * the serial driver will be extracting data from the circular buffer and modifying
@@ -684,7 +686,7 @@ static inline int usbclass_recvpacket(FAR struct usbser_dev_s *priv,
    * then we have overrun the serial driver and data will be lost.
    */
 
-  while (nexthead != recv->tail && reqlen > 0)
+  while (nexthead != recv->tail && nbytes < reqlen)
     {
       /* Copy one byte to the head of the circular RX buffer */
 
@@ -693,21 +695,7 @@ static inline int usbclass_recvpacket(FAR struct usbser_dev_s *priv,
       /* Update counts and indices */
 
       currhead = nexthead;
-      reqlen--;
-
-      /* Wake up the serial driver if it is waiting for incoming data. If we
-       * are running in an interrupt handler, then the serial driver will
-       * not run until the interrupt handler returns.  But we will exercise
-       * care in the following just in case the serial driver does run.
-       */
-
-      if (priv->rxenabled && serdev->recvwaiting)
-        {
-          recv->head          = currhead;
-          serdev->recvwaiting = FALSE;
-          sem_post(&serdev->recvsem);
-          currhead            = recv->head;
-        }
+      nbytes++;
 
       /* Increment the head index and check for wrap around */
 
@@ -731,9 +719,20 @@ static inline int usbclass_recvpacket(FAR struct usbser_dev_s *priv,
       priv->rxhead = currhead;
     }
 
+  /* If data was added to the incoming serial buffer, then wake up any
+   * threads is waiting for incoming data. If we are running in an interrupt
+   * handler, then the serial driver will not run until the interrupt handler
+   * returns.
+   */
+
+  if (priv->rxenabled && nbytes > 0)
+    {
+      uart_datareceived(serdev);
+    }
+
   /* Return an error if the entire packet could not be transferred */
 
-  if (reqlen > 0)
+  if (nbytes < reqlen)
     {
       usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RXOVERRUN), 0);
       return -ENOSPC;
@@ -2017,15 +2016,9 @@ static void usbser_rxint(FAR struct uart_dev_s *dev, boolean enable)
             {
               serdev->recv.head = priv->rxhead;
 
-              /* Is the serial driver waiting for more data? */
+              /* Yes... signal the availability of new data */
 
-              if (serdev->recvwaiting)
-                {
-                  /* Yes... signal the availability of new data */
-
-                  sem_post(&serdev->recvsem);
-                  serdev->recvwaiting = FALSE;
-                }
+              uart_datareceived(serdev);
             }
 
           /* RX "interrupts are no longer disabled */
diff --git a/nuttx/examples/poll/poll_listener.c b/nuttx/examples/poll/poll_listener.c
index 6182ca0de..c798b6e88 100644
--- a/nuttx/examples/poll/poll_listener.c
+++ b/nuttx/examples/poll/poll_listener.c
@@ -57,6 +57,17 @@
  * Definitions
  ****************************************************************************/
 
+#if defined(CONFIG_DEV_CONSOLE) && !defined(CONFIG_DEV_LOWCONSOLE)
+#   define HAVE_CONSOLE
+#   define NPOLLFDS 2
+#   define CONSNDX  0
+#   define FIFONDX  1
+#else
+#   undef  HAVE_CONSOLE
+#   define NPOLLFDS 1
+#   define FIFONDX  0
+#endif
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -79,13 +90,15 @@
 
 void *poll_listener(pthread_addr_t pvarg)
 {
-  struct pollfd fds;
+  struct pollfd fds[NPOLLFDS];
   char buffer[64];
   ssize_t nbytes;
   boolean timeout;
   boolean pollin;
+  int nevents;
   int fd;
   int ret;
+  int i;
 
   /* Open the FIFO for non-blocking read */
 
@@ -105,15 +118,20 @@ void *poll_listener(pthread_addr_t pvarg)
     {
       message("poll_listener: Calling poll()\n");
 
-      memset(&fds, 0, sizeof(struct pollfd));
-      fds.fd      = fd;
-      fds.events  = POLLIN;
-      fds.revents = 0;
+      memset(fds, 0, sizeof(struct pollfd)*NPOLLFDS);
+#ifdef HAVE_CONSOLE
+      fds[CONSNDX].fd      = 0;
+      fds[CONSNDX].events  = POLLIN;
+      fds[CONSNDX].revents = 0;
+#endif
+      fds[FIFONDX].fd      = fd;
+      fds[FIFONDX].events  = POLLIN;
+      fds[FIFONDX].revents = 0;
 
-      timeout     = FALSE;
-      pollin      = FALSE;
+      timeout              = FALSE;
+      pollin               = FALSE;
 
-      ret = poll(&fds, 1, POLL_LISTENER_DELAY);
+      ret = poll(fds, NPOLLFDS, POLL_LISTENER_DELAY);
 
       message("\npoll_listener: poll returned: %d\n", ret);
       if (ret < 0)
@@ -122,71 +140,116 @@ void *poll_listener(pthread_addr_t pvarg)
         }
       else if (ret == 0)
         {
-          message("poll_listener: Timeout, revents=%02x\n", fds.revents);
+          message("poll_listener: Timeout\n");
           timeout = TRUE;
-          if (fds.revents != 0)
-            {
-              message("poll_listener: ERROR? expected revents=00, received revents=%02x\n",
-                      fds.revents);
-            }
+        }
+      else if (ret > NPOLLFDS)
+        {
+          message("poll_listener: ERROR poll reported: %d\n");
         }
       else
         {
-          if (ret != 1)
+          pollin = TRUE;
+        }
+
+      nevents = 0;
+      for (i = 0; i < NPOLLFDS; i++)
+        {
+          message("poll_listener: FIFO revents[%d]=%02x\n", i, fds[i].revents);
+          if (timeout)
             {
-              message("poll_listener: ERROR poll reported: %d\n");
+              if (fds[i].revents != 0)
+                {
+                  message("poll_listener: ERROR? expected revents=00, received revents[%d]=%02x\n",
+                          fds[i].revents, i);
+                }
             }
-          else
+          else if (pollin)
             {
-              pollin = TRUE;
+               if (fds[i].revents == POLLIN)
+                 {
+                   nevents++;
+                 }
+               else if (fds[i].revents != 0)
+                {
+                   message("poll_listener: ERROR unexpected revents[i]=%02x\n",
+                           i, fds[i].revents);
+                 }
             }
+        }
 
-          message("poll_listener: revents=%02x\n", fds.revents);
-          if (fds.revents != POLLIN)
-            {
-              message("poll_listener: ERROR expected revents=%02x, received revents=%02x\n",
-                      fds.revents);
-              message("               (might just be a race condition)\n");
-            }
+      if (pollin && nevents != ret)
+        {
+           message("poll_listener: ERROR found %d events, poll reported %d\n", nevents, ret);
         }
 
-      /* In any event, read until the pipe is empty */
+      /* In any event, read until the pipe/serial  is empty */
 
-      do
+      for (i = 0; i < NPOLLFDS; i++)
         {
-          nbytes = read(fd, buffer, 63);
-          if (nbytes <= 0)
+          do
             {
-              if (nbytes == 0 || errno == EAGAIN)
+#ifdef HAVE_CONSOLE
+              /* Hack to work around the fact that the console driver on the
+               * simulator is always non-blocking.
+               */
+
+              if (i == CONSNDX)
                 {
-                  if (pollin)
+                  if ((fds[CONSNDX].revents & POLLIN) != 0)
+                    {
+                      buffer[0] = getchar();
+                      nbytes = 1;
+                    }
+                  else
                     {
-                      message("poll_listener: ERROR no read data\n");
+                      nbytes = 0;
                     }
                 }
-              else if (errno != EINTR)
+              else
+#endif
                 {
-                  message("poll_listener: read failed: %d\n", errno);
+                  /* The pipe works differently, it returns whatever data
+                   * it has available without blocking.
+                   */
+
+                  nbytes = read(fds[i].fd, buffer, 63);
                 }
-              nbytes = 0;
-            }
-          else
-            {
-              if (timeout)
+
+              if (nbytes <= 0)
                 {
-                  message("poll_listener: ERROR? Poll timeout, but data read\n");
-                  message("               (might just be a race condition)\n");
+                  if (nbytes == 0 || errno == EAGAIN)
+                    {
+                      if ((fds[i].revents & POLLIN) != 0)
+                        {
+                          message("poll_listener: ERROR no read data[%d]\n", i);
+                        }
+                    }
+                  else if (errno != EINTR)
+                    {
+                      message("poll_listener: read[%d] failed: %d\n", i, errno);
+                    }
+                  nbytes = 0;
                 }
+              else
+                {
+                  if (timeout)
+                    {
+                      message("poll_listener: ERROR? Poll timeout, but data read[%d]\n", i);
+                      message("               (might just be a race condition)\n");
+                    }
 
-              buffer[nbytes] = '\0';
-              message("poll_listener: Read '%s' (%d bytes)\n", buffer, nbytes);
-            }
+                  buffer[nbytes] = '\0';
+                  message("poll_listener: Read[%d] '%s' (%d bytes)\n", i, buffer, nbytes);
+                }
 
-          timeout = FALSE;
-          pollin  = FALSE;
-        }
-      while (nbytes > 0);
+              /* Suppress error report if no read data on the next time through */
 
+              fds[i].revents = 0;
+            }
+          while (nbytes > 0);
+        }
+ 
       /* Make sure that everything is displayed */
 
       msgflush();
diff --git a/nuttx/include/nuttx/serial.h b/nuttx/include/nuttx/serial.h
index 9954c16c0..ed5c6a1c0 100644
--- a/nuttx/include/nuttx/serial.h
+++ b/nuttx/include/nuttx/serial.h
@@ -49,6 +49,14 @@
  * Definitions
  ************************************************************************************/
 
+/* Maximum number of threads than can be waiting for POLL events */
+
+#ifndef CONFIG_DEV_CONSOLE_NPOLLWAITERS
+#  define CONFIG_DEV_CONSOLE_NPOLLWAITERS 2
+#endif
+
+/* vtable access helpers */
+
 #define uart_setup(dev)          dev->ops->setup(dev)
 #define uart_shutdown(dev)       dev->ops->shutdown(dev)
 #define uart_attach(dev)         dev->ops->attach(dev)
@@ -186,10 +194,23 @@ struct uart_dev_s
   sem_t                closesem;    /* Locks out new open while close is in progress */
   sem_t                xmitsem;     /* Wakeup user waiting for space in xmit.buffer */
   sem_t                recvsem;     /* Wakeup user waiting for data in recv.buffer */
+#ifndef CONFIG_DISABLE_POLL
+  sem_t                pollsem;     /* Manages exclusive access to fds[] */
+#endif
   struct uart_buffer_s xmit;        /* Describes transmit buffer */
   struct uart_buffer_s recv;        /* Describes receive buffer */
   FAR const struct uart_ops_s *ops; /* Arch-specific operations */
-  FAR void            *priv;       /* Used by the arch-specific logic */
+  FAR void            *priv;        /* Used by the arch-specific logic */
+
+  /* The following is a list if poll structures of threads waiting for
+   * driver events. The 'struct pollfd' reference for each open is also
+   * retained in the f_priv field of the 'struct file'.
+   */
+
+#ifndef CONFIG_DISABLE_POLL
+  struct pollfd *fds[CONFIG_DEV_CONSOLE_NPOLLWAITERS];
+#endif
+
 };
 typedef struct uart_dev_s uart_dev_t;
 
@@ -245,6 +266,31 @@ EXTERN void uart_xmitchars(FAR uart_dev_t *dev);
 
 EXTERN void uart_recvchars(FAR uart_dev_t *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.
+ *
+ ************************************************************************************/
+
+EXTERN void uart_datareceived(FAR uart_dev_t *dev);
+
+/************************************************************************************
+ * 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.
+ *
+ ************************************************************************************/
+
+EXTERN void uart_datasent(FAR uart_dev_t *dev);
+
 #undef EXTERN
 #if defined(__cplusplus)
 }