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uiomove (9)
  • uiomove (9) ( Solaris man: Ядро )
  • >> uiomove (9) ( FreeBSD man: Ядро )

  • BSD mandoc
     

    NAME

    uio
    
     
    uiomove
    
     - device driver I/O routines
    
     
    

    SYNOPSIS

       #include <sys/types.h>
       #include <sys/uio.h>

    struct uio {
            struct  iovec *uio_iov;         /* scatter/gather list */
            int     uio_iovcnt;             /* length of scatter/gather list */
            off_t   uio_offset;             /* offset in target object */
            int     uio_resid;              /* remaining bytes to copy */
            enum    uio_seg uio_segflg;     /* address space */
            enum    uio_rw uio_rw;          /* operation */
            struct  thread *uio_td;         /* owner */
    };
    
    int uiomove (void *buf int howmuch struct uio *uiop);
     

    DESCRIPTION

    The function uiomove ();
    is used to handle transfer of data between buffers and I/O vectors that might possibly also cross the user/kernel space boundary.

    As a result of any read(2), write(2), readv(2), or writev(2) system call that is being passed to a character-device driver, the appropriate driver d_read or d_write entry will be called with a pointer to a Vt struct uio being passed. The transfer request is encoded in this structure. The driver itself should use uiomove ();
    to get at the data in this structure.

    The fields in the Vt uio structure are:

    uio_iov
    The array of I/O vectors to be processed. In the case of scatter/gather I/O, this will be more than one vector.
    uio_iovcnt
    The number of I/O vectors present.
    uio_offset
    The offset into the device.
    uio_resid
    The remaining number of bytes to process, updated after transfer.
    uio_segflg
    One of the following flags:

    UIO_USERSPACE
    The I/O vector points into a process's address space.
    UIO_SYSSPACE
    The I/O vector points into the kernel address space.
    UIO_NOCOPY
    Do not copy, already in object.

    uio_rw
    The direction of the desired transfer, either UIO_READ or UIO_WRITE
    uio_td
    The pointer to a Vt struct thread for the associated thread; used if uio_segflg indicates that the transfer is to be made from/to a process's address space.

     

    RETURN VALUES

    On success uiomove ();
    will return 0, on error it will return an appropriate errno.  

    ERRORS

    uiomove ();
    will fail and return the following error code if:

    Bq Er EFAULT
    The invoked copyin(9) or copyout(9) returned Er EFAULT
     

    EXAMPLES

    The idea is that the driver maintains a private buffer for its data, and processes the request in chunks of maximal the size of this buffer. Note that the buffer handling below is very simplified and will not work (the buffer pointer is not being advanced in case of a partial read), it is just here to demonstrate the handling.
    /* MIN() can be found there: */
    #include <sys/param.h>
    
    #define BUFSIZE 512
    static char buffer[BUFSIZE];
    
    static int data_available;      /* amount of data that can be read */
    
    static int
    fooread(dev_t dev, struct uio *uio, int flag)
    {
            int rv, amnt;
    
            rv = 0;
            while (uio->uio_resid > 0) {
                    if (data_available > 0) {
                            amnt = MIN(uio->uio_resid, data_available);
                            rv = uiomove(buffer, amnt, uio);
                            if (rv != 0)
                                    break;
                            data_available -= amnt;
                    } else
                            tsleep(...);    /* wait for a better time */
            }
            if (rv != 0) {
                    /* do error cleanup here */
            }
            return (rv);
    }
    
     

    SEE ALSO

    read(2), readv(2), write(2), writev(2), copyin(9), copyout(9), sleep(9)  

    HISTORY

    The mechanism appeared in some early version of UNIX  

    AUTHORS

    This manual page was written by An J:org Wunsch .


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    EXAMPLES
    SEE ALSO
    HISTORY
    AUTHORS


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