uio_resid api tweak

* add uio_resid member to struct uio

* retire uio_resid() function

* move the overflow check into uio_init

* change the error number on the overflow from EOVERFLOW to EINVAL
  to match NetBSD

drivers/loop/loop.c

@@ -85,12 +85,9 @@ static ssize_t loop_writev(FAR struct file *filep, FAR struct uio *uio)
 {
   /* Say that everything was written */
 
-  ssize_t ret = uio_resid(uio);
-  if (ret >= 0)
-    {
-      uio_advance(uio, ret);
-    }
+  size_t ret = uio->uio_resid;
 
+  uio_advance(uio, ret);
   return ret;
 }
 

drivers/misc/dev_null.c

@@ -88,12 +88,11 @@ static ssize_t devnull_writev(FAR struct file *filep, FAR struct uio *uio)
 {
   UNUSED(filep);
 
-  ssize_t ret = uio_resid(uio); /* Say that everything was written */
-  if (ret >= 0)
-    {
-      uio_advance(uio, ret);
-    }
+  /* Say that everything was written */
+
+  size_t ret = uio->uio_resid;
 
+  uio_advance(uio, ret);
   return ret;
 }
 

drivers/misc/dev_zero.c

@@ -74,18 +74,13 @@ static const struct file_operations g_devzero_fops =
 
 static ssize_t devzero_readv(FAR struct file *filep, FAR struct uio *uio)
 {
-  ssize_t total =  uio_resid(uio);
+  size_t total = uio->uio_resid;
   FAR const struct iovec *iov = uio->uio_iov;
   int iovcnt = uio->uio_iovcnt;
   int i;
 
   UNUSED(filep);
 
-  if (total < 0)
-    {
-      return total;
-    }
-
   for (i = 0; i < iovcnt; i++)
     {
       memset(iov[i].iov_base, 0, iov[i].iov_len);
@@ -102,15 +97,12 @@ static ssize_t devzero_readv(FAR struct file *filep, FAR struct uio *uio)
 
 static ssize_t devzero_writev(FAR struct file *filep, FAR struct uio *uio)
 {
-  ssize_t total;
+  size_t total;
   UNUSED(filep);
 
-  total = uio_resid(uio);
-  if (total >= 0)
-    {
-      uio_advance(uio, total);
-    }
+  total = uio->uio_resid;
 
+  uio_advance(uio, total);
   return total;
 }
 

drivers/serial/serial.c

@@ -910,12 +910,6 @@ static ssize_t uart_readv(FAR struct file *filep, FAR struct uio *uio)
   char ch;
   int ret;
 
-  buflen = uio_resid(uio);
-  if (buflen < 0)
-    {
-      return buflen;
-    }
-
   /* Only one user can access rxbuf->tail at a time */
 
   ret = nxmutex_lock(&dev->recv.lock);
@@ -934,6 +928,7 @@ static ssize_t uart_readv(FAR struct file *filep, FAR struct uio *uio)
    * data from the end of the buffer.
    */
 
+  buflen = uio->uio_resid;
   while (recvd < buflen)
     {
 #ifdef CONFIG_SERIAL_REMOVABLE
@@ -1424,11 +1419,7 @@ static ssize_t uart_writev(FAR struct file *filep, FAR struct uio *uio)
       return ret;
     }
 
-  buflen = nwritten = uio_resid(uio);
-  if (nwritten < 0)
-    {
-      return nwritten;
-    }
+  buflen = nwritten = uio->uio_resid;
 
   /* Only one user can access dev->xmit.head at a time */
 

fs/vfs/fs_read.c

@@ -208,10 +208,16 @@ ssize_t file_read(FAR struct file *filep, FAR void *buf, size_t nbytes)
 {
   struct iovec iov;
   struct uio uio;
+  ssize_t ret;
 
   iov.iov_base = buf;
   iov.iov_len = nbytes;
-  uio_init(&uio, &iov, 1);
+  ret = uio_init(&uio, &iov, 1);
+  if (ret != 0)
+    {
+      return ret;
+    }
+
   return file_readv(filep, &uio);
 }
 
@@ -254,8 +260,12 @@ ssize_t nx_readv(int fd, FAR const struct iovec *iov, int iovcnt)
 
   /* Then let file_readv do all of the work. */
 
-  uio_init(&uio, iov, iovcnt);
-  ret = file_readv(filep, &uio);
+  ret = uio_init(&uio, iov, iovcnt);
+  if (ret == 0)
+    {
+      ret = file_readv(filep, &uio);
+    }
+
   fs_putfilep(filep);
   return ret;
 }

fs/vfs/fs_uio.c

@@ -35,19 +35,19 @@
 #include <errno.h>
 
 /****************************************************************************
- * Public Functions
+ * Private Functions
  ****************************************************************************/
 
 /****************************************************************************
- * Name: uio_resid
+ * Name: uio_calc_resid
  *
  * Description:
  *   Return the remaining length of data in bytes.
- *   Or -EOVERFLOW.
+ *   Or -EINVAL.
  *
  ****************************************************************************/
 
-ssize_t uio_resid(FAR const struct uio *uio)
+ssize_t uio_calc_resid(FAR const struct uio *uio)
 {
   const struct iovec *iov = uio->uio_iov;
   int iovcnt = uio->uio_iovcnt;
@@ -60,7 +60,7 @@ ssize_t uio_resid(FAR const struct uio *uio)
       DEBUGASSERT(offset_in_iov <= iov[i].iov_len);
       if (SSIZE_MAX - len < iov[i].iov_len - offset_in_iov)
         {
-          return -EOVERFLOW;
+          return -EINVAL;
         }
 
       len += iov[i].iov_len - offset_in_iov;
@@ -70,6 +70,10 @@ ssize_t uio_resid(FAR const struct uio *uio)
   return len;
 }
 
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
 /****************************************************************************
  * Name: uio_advance
  *
@@ -84,7 +88,9 @@ void uio_advance(FAR struct uio *uio, size_t sz)
   int iovcnt = uio->uio_iovcnt;
   size_t offset_in_iov = uio->uio_offset_in_iov;
 
-  DEBUGASSERT(sz <= uio_resid(uio));
+  DEBUGASSERT(sz <= SSIZE_MAX);
+  DEBUGASSERT(uio->uio_resid <= SSIZE_MAX);
+  DEBUGASSERT(sz <= uio->uio_resid);
   while (iovcnt > 0)
     {
       DEBUGASSERT(offset_in_iov <= iov->iov_len);
@@ -113,11 +119,18 @@ void uio_advance(FAR struct uio *uio, size_t sz)
  *
  ****************************************************************************/
 
-void uio_init(FAR struct uio *uio, FAR const struct iovec *iov, int iovcnt)
+int uio_init(FAR struct uio *uio, FAR const struct iovec *iov, int iovcnt)
 {
   memset(uio, 0, sizeof(*uio));
   uio->uio_iov = iov;
   uio->uio_iovcnt = iovcnt;
+  uio->uio_resid = uio_calc_resid(uio);
+  if (uio->uio_resid < 0)
+    {
+      return -EINVAL;
+    }
+
+  return 0;
 }
 
 /****************************************************************************
@@ -133,9 +146,10 @@ void uio_copyfrom(FAR struct uio *uio, size_t offset, FAR const void *buf,
 {
   FAR const struct iovec *iov = uio->uio_iov;
 
-  DEBUGASSERT(uio_resid(uio) >= 0);
-  DEBUGASSERT(len <= uio_resid(uio));
-  DEBUGASSERT(offset <= uio_resid(uio) - len);
+  DEBUGASSERT(uio->uio_resid >= 0);
+  DEBUGASSERT(uio->uio_resid <= SSIZE_MAX);
+  DEBUGASSERT(len <= uio->uio_resid);
+  DEBUGASSERT(offset <= uio->uio_resid - len);
   DEBUGASSERT(SSIZE_MAX - offset >= uio->uio_offset_in_iov);
 
   offset += uio->uio_offset_in_iov;
@@ -180,9 +194,10 @@ void uio_copyto(FAR struct uio *uio, size_t offset, FAR void *buf,
 {
   FAR const struct iovec *iov = uio->uio_iov;
 
-  DEBUGASSERT(uio_resid(uio) >= 0);
-  DEBUGASSERT(len <= uio_resid(uio));
-  DEBUGASSERT(offset <= uio_resid(uio) - len);
+  DEBUGASSERT(uio->uio_resid >= 0);
+  DEBUGASSERT(uio->uio_resid <= SSIZE_MAX);
+  DEBUGASSERT(len <= uio->uio_resid);
+  DEBUGASSERT(offset <= uio->uio_resid - len);
   DEBUGASSERT(SSIZE_MAX - offset >= uio->uio_offset_in_iov);
 
   offset += uio->uio_offset_in_iov;

fs/vfs/fs_write.c

@@ -207,10 +207,16 @@ ssize_t file_write(FAR struct file *filep, FAR const void *buf,
 {
   struct iovec iov;
   struct uio uio;
+  ssize_t ret;
 
   iov.iov_base = (FAR void *)buf;
   iov.iov_len = nbytes;
-  uio_init(&uio, &iov, 1);
+  ret = uio_init(&uio, &iov, 1);
+  if (ret != 0)
+    {
+      return ret;
+    }
+
   return file_writev(filep, &uio);
 }
 
@@ -256,8 +262,12 @@ ssize_t nx_writev(int fd, FAR const struct iovec *iov, int iovcnt)
        * index.  Note that file_writev() will return the errno on failure.
        */
 
-      uio_init(&uio, iov, iovcnt);
-      ret = file_writev(filep, &uio);
+      ret = uio_init(&uio, iov, iovcnt);
+      if (ret == 0)
+        {
+          ret = file_writev(filep, &uio);
+        }
+
       fs_putfilep(filep);
     }
 

include/nuttx/fs/uio.h

@@ -45,24 +45,14 @@ struct uio
 {
   FAR const struct iovec *uio_iov;
   int uio_iovcnt;
+  size_t uio_resid;         /* the remaining bytes in the request */
   size_t uio_offset_in_iov; /* offset in uio_iov[0].iov_base */
 };
 
 /****************************************************************************
  * Public Function Prototypes
  ****************************************************************************/
 
-/****************************************************************************
- * Name: uio_resid
- *
- * Description:
- *   Return the remaining length of data in bytes.
- *   Or -EOVERFLOW.
- *
- ****************************************************************************/
-
-ssize_t uio_resid(FAR const struct uio *uio);
-
 /****************************************************************************
  * Name: uio_advance
  *
@@ -79,9 +69,16 @@ void uio_advance(FAR struct uio *uio, size_t sz);
  * Description:
  *   Initialize the uio structure with reasonable default values.
  *
+ * Return Value:
+ *   0 on success. A negative error number on an error.
+ *
+ *   -EINVAL: The total size of the given iovec is too large.
+ *            (Note: NetBSD's readv returns EINVAL in that case.
+ *            I (yamamoto) couldn't find the specification in POSIX.)
+ *
  ****************************************************************************/
 
-void uio_init(FAR struct uio *uio, FAR const struct iovec *iov, int iovcnt);
+int uio_init(FAR struct uio *uio, FAR const struct iovec *iov, int iovcnt);
 
 /****************************************************************************
  * Name: uio_copyto