drivers/serial/serial.c: adapt readv api to avoid block on secound re…

…ad in readv()

Signed-off-by: chao an <[email protected]>

drivers/serial/serial.c

@@ -115,6 +115,7 @@ static ssize_t uart_read(FAR struct file *filep,
 static ssize_t uart_write(FAR struct file *filep,
                           FAR const char *buffer,
                           size_t buflen);
+static ssize_t uart_readv(FAR struct file *filep, FAR struct uio *uio);
 static int     uart_ioctl(FAR struct file *filep,
                           int cmd, unsigned long arg);
 static int     uart_poll(FAR struct file *filep,
@@ -148,7 +149,7 @@ static const struct file_operations g_serialops =
   NULL,         /* mmap */
   NULL,         /* truncate */
   uart_poll,    /* poll */
-  NULL,         /* readv */
+  uart_readv,   /* readv */
   NULL          /* writev */
 #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
   , uart_unlink /* unlink */
@@ -850,8 +851,8 @@ static int uart_close(FAR struct file *filep)
  * Name: uart_read
  ****************************************************************************/
 
-static ssize_t uart_read(FAR struct file *filep,
-                         FAR char *buffer, size_t buflen)
+static ssize_t uart_read_internal(FAR struct file *filep, FAR char *buffer,
+                                  size_t buflen, bool nonblock)
 {
   FAR struct inode *inode = filep->f_inode;
   FAR uart_dev_t *dev = inode->i_private;
@@ -1060,7 +1061,7 @@ static ssize_t uart_read(FAR struct file *filep,
        * return what we have.
        */
 
-      else if ((filep->f_oflags & O_NONBLOCK) != 0)
+      else if ((filep->f_oflags & O_NONBLOCK) != 0 || nonblock)
         {
           /* If nothing was transferred, then return the -EAGAIN
            * error (not zero which means end of file).
@@ -1102,7 +1103,7 @@ static ssize_t uart_read(FAR struct file *filep,
        * wait.
        */
 
-      else if ((filep->f_oflags & O_NONBLOCK) != 0)
+      else if ((filep->f_oflags & O_NONBLOCK) != 0 || nonblock)
         {
           /* Break out of the loop returning -EAGAIN */
 
@@ -1328,6 +1329,58 @@ static ssize_t uart_read(FAR struct file *filep,
   return recvd;
 }
 
+static ssize_t uart_read(FAR struct file *filep,
+                         FAR char *buffer, size_t buflen)
+{
+  return uart_read_internal(filep, buffer, buflen, false);
+}
+
+/****************************************************************************
+ * Name: uart_readv
+ ****************************************************************************/
+
+static ssize_t uart_readv(FAR struct file *filep, FAR struct uio *uio)
+{
+  FAR const struct iovec *iov = uio->uio_iov;
+  int iovcnt = uio->uio_iovcnt;
+  bool nonblock = false;
+  ssize_t ntotal;
+  ssize_t nread;
+  int i;
+
+  for (i = 0, ntotal = 0; i < iovcnt; i++)
+    {
+      nread = uart_read_internal(filep, iov[i].iov_base,
+                                 iov[i].iov_len, nonblock);
+      if (nread < 0)
+        {
+          if (ntotal > 0)
+            {
+              break;
+            }
+
+          return nread;
+        }
+
+      ntotal += nread;
+
+      /* Check for a parital success condition, including an end-of-file */
+
+      if (nread < iov[i].iov_len)
+        {
+          break;
+        }
+
+      /* set nonblock flag after first read */
+
+      nonblock = true;
+    }
+
+  uio_advance(uio, ntotal);
+
+  return ntotal;
+}
+
 /****************************************************************************
  * Name: uart_write
  ****************************************************************************/