uio(9s) [osf1 man page]

uio(9s) 																   uio(9s)

NAME

       uio - General: Describes I/O, either single vector or multiple vectors

SYNOPSIS

       -----------------------------
       Member Name   Data Type
       -----------------------------
       uio_iov	     struct iovec *
       uio_iovcnt    int
       uio_offset    off_t
       uio_segflg    enum uio_seg
       uio_resid     int
       uio_rw	     enum uio_rw
       -----------------------------

MEMBERS

       Specifies  a  pointer  to the first iovec structure. The iovec structure has two members: one that specifies the address of the segment and
       another that specifies the size of the segment. The system allocates contiguous iovec structures for a given transfer.  Specifies the  num-
       ber  of	iovec  structures for this transfer.  Specifies the offset within the file.  Specifies the segment type. This member can be set to
       one of the following values: UIO_USERSPACE (the segment is from the user data space), UIO_SYSSPACE (the segment is from the system  space),
       or  UIO_USERISPACE  (the  segment  is  from the user I space).  Specifies the number of bytes that still need to be transferred.  Specifies
       whether the transfer is a read or a write. This member is set by read and write system calls according to the corresponding  field  in  the
       file  descriptor. This member can be set to one of the following values: UIO_READ (read transfer), UIO_WRITE (write transfer), or UIO_AIORW
       (Alpha I/O read/write transfer).

DESCRIPTION

       The uio data structure describes, either singler-vector or multiple-vector I/O. Typically, kernel modules do not manipulate the members	of
       this  data structure. However, the data structure is presented here for the purpose of understanding the uiomove routine, which operates on
       the members of the uio structure.

FILES

SEE ALSO

       Routines: uiomove(9r)

																	   uio(9s)

UIOMOVE(9)						   BSD Kernel Developer's Manual						UIOMOVE(9)

NAME

     uiomove -- move data described by a struct uio

SYNOPSIS

     #include <sys/systm.h>

     int
     uiomove(void *buf, size_t n, struct uio *uio);

DESCRIPTION

     The uiomove() function copies up to n bytes between the kernel-space address pointed to by buf and the addresses described by uio, which may
     be in user-space or kernel-space.

     The uio argument is a pointer to a struct uio as defined by <sys/uio.h>:

	   struct uio {
		   struct  iovec *uio_iov;
		   int	   uio_iovcnt;
		   off_t   uio_offset;
		   size_t  uio_resid;
		   enum    uio_rw uio_rw;
		   struct  vmspace *uio_vmspace;
	   };

     A struct uio typically describes data in motion.  Several of the fields described below reflect that expectation.

     uio_iov	   Pointer to array of I/O vectors to be processed.  The struct iovec is defined to be:

			 struct iovec {
				 void	 *iov_base;
				 size_t   iov_len;
			 };

		   The members in the struct iovec should only be initialized.	These are:

			 iov_base    The address for a range of memory to or from which data is transferred.

			 iov_len     The number of bytes of data to be transferred to or from the range of memory starting at iov_base.

     uio_iovcnt    The number of I/O vectors in the uio_iov array.

     uio_offset    An offset into the corresponding object.

     uio_resid	   The amount of space described by the structure; notionally, the amount of data remaining to be transferred.

     uio_rw	   A flag indicating whether data should be read into the space (UIO_READ) or written from the space (UIO_WRITE).

     uio_vmspace   A pointer to the address space which is being transferred to or from.

     The value of uio->uio_rw controls whether uiomove() copies data from buf to uio or vice versa.

     The lesser of n or uio->uio_resid bytes are copied.

     uiomove() changes fields of the structure pointed to by uio, such that uio->uio_resid is decremented by the amount of data moved,
     uio->uio_offset is incremented by the same amount, and the array of iovecs is adjusted to point that much farther into the region described.
     This allows multiple calls to uiomove() to easily be used to fill or drain the region of data.

RETURN VALUES

     Upon successful completion, uiomove() returns 0.  If a bad address is encountered, EFAULT is returned.

SEE ALSO

     copy(9), fetch(9), store(9)

BSD
								  April 26, 2010							       BSD